2005-04-17 05:20:36 +07:00
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|
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/*
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* linux/kernel/timer.c
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*
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2013-05-01 05:27:37 +07:00
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* Kernel internal timers
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2005-04-17 05:20:36 +07:00
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*
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* 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
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*
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* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
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* "A Kernel Model for Precision Timekeeping" by Dave Mills
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* 1998-12-24 Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
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* serialize accesses to xtime/lost_ticks).
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* Copyright (C) 1998 Andrea Arcangeli
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* 1999-03-10 Improved NTP compatibility by Ulrich Windl
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* 2002-05-31 Move sys_sysinfo here and make its locking sane, Robert Love
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* 2000-10-05 Implemented scalable SMP per-CPU timer handling.
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* Copyright (C) 2000, 2001, 2002 Ingo Molnar
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* Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
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*/
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#include <linux/kernel_stat.h>
|
2011-05-24 01:51:41 +07:00
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#include <linux/export.h>
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2005-04-17 05:20:36 +07:00
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#include <linux/interrupt.h>
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#include <linux/percpu.h>
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#include <linux/init.h>
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#include <linux/mm.h>
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#include <linux/swap.h>
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2007-10-19 13:40:14 +07:00
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#include <linux/pid_namespace.h>
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2005-04-17 05:20:36 +07:00
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#include <linux/notifier.h>
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#include <linux/thread_info.h>
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#include <linux/time.h>
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#include <linux/jiffies.h>
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#include <linux/posix-timers.h>
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#include <linux/cpu.h>
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#include <linux/syscalls.h>
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2006-01-08 16:02:17 +07:00
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#include <linux/delay.h>
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2007-02-16 16:28:03 +07:00
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#include <linux/tick.h>
|
[PATCH] Add debugging feature /proc/timer_stat
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.
Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec
[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 16:28:13 +07:00
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#include <linux/kallsyms.h>
|
2010-10-14 13:01:34 +07:00
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#include <linux/irq_work.h>
|
2009-04-16 13:46:41 +07:00
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#include <linux/sched.h>
|
2013-02-07 22:46:59 +07:00
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#include <linux/sched/sysctl.h>
|
include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h
percpu.h is included by sched.h and module.h and thus ends up being
included when building most .c files. percpu.h includes slab.h which
in turn includes gfp.h making everything defined by the two files
universally available and complicating inclusion dependencies.
percpu.h -> slab.h dependency is about to be removed. Prepare for
this change by updating users of gfp and slab facilities include those
headers directly instead of assuming availability. As this conversion
needs to touch large number of source files, the following script is
used as the basis of conversion.
http://userweb.kernel.org/~tj/misc/slabh-sweep.py
The script does the followings.
* Scan files for gfp and slab usages and update includes such that
only the necessary includes are there. ie. if only gfp is used,
gfp.h, if slab is used, slab.h.
* When the script inserts a new include, it looks at the include
blocks and try to put the new include such that its order conforms
to its surrounding. It's put in the include block which contains
core kernel includes, in the same order that the rest are ordered -
alphabetical, Christmas tree, rev-Xmas-tree or at the end if there
doesn't seem to be any matching order.
* If the script can't find a place to put a new include (mostly
because the file doesn't have fitting include block), it prints out
an error message indicating which .h file needs to be added to the
file.
The conversion was done in the following steps.
1. The initial automatic conversion of all .c files updated slightly
over 4000 files, deleting around 700 includes and adding ~480 gfp.h
and ~3000 slab.h inclusions. The script emitted errors for ~400
files.
2. Each error was manually checked. Some didn't need the inclusion,
some needed manual addition while adding it to implementation .h or
embedding .c file was more appropriate for others. This step added
inclusions to around 150 files.
3. The script was run again and the output was compared to the edits
from #2 to make sure no file was left behind.
4. Several build tests were done and a couple of problems were fixed.
e.g. lib/decompress_*.c used malloc/free() wrappers around slab
APIs requiring slab.h to be added manually.
5. The script was run on all .h files but without automatically
editing them as sprinkling gfp.h and slab.h inclusions around .h
files could easily lead to inclusion dependency hell. Most gfp.h
inclusion directives were ignored as stuff from gfp.h was usually
wildly available and often used in preprocessor macros. Each
slab.h inclusion directive was examined and added manually as
necessary.
6. percpu.h was updated not to include slab.h.
7. Build test were done on the following configurations and failures
were fixed. CONFIG_GCOV_KERNEL was turned off for all tests (as my
distributed build env didn't work with gcov compiles) and a few
more options had to be turned off depending on archs to make things
build (like ipr on powerpc/64 which failed due to missing writeq).
* x86 and x86_64 UP and SMP allmodconfig and a custom test config.
* powerpc and powerpc64 SMP allmodconfig
* sparc and sparc64 SMP allmodconfig
* ia64 SMP allmodconfig
* s390 SMP allmodconfig
* alpha SMP allmodconfig
* um on x86_64 SMP allmodconfig
8. percpu.h modifications were reverted so that it could be applied as
a separate patch and serve as bisection point.
Given the fact that I had only a couple of failures from tests on step
6, I'm fairly confident about the coverage of this conversion patch.
If there is a breakage, it's likely to be something in one of the arch
headers which should be easily discoverable easily on most builds of
the specific arch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Guess-its-ok-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
2010-03-24 15:04:11 +07:00
|
|
|
#include <linux/slab.h>
|
2013-05-01 05:27:34 +07:00
|
|
|
#include <linux/compat.h>
|
2005-04-17 05:20:36 +07:00
|
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#include <asm/uaccess.h>
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#include <asm/unistd.h>
|
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|
#include <asm/div64.h>
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|
#include <asm/timex.h>
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|
#include <asm/io.h>
|
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|
|
|
2009-08-10 09:48:59 +07:00
|
|
|
#define CREATE_TRACE_POINTS
|
|
|
|
#include <trace/events/timer.h>
|
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|
|
|
2014-02-08 14:51:59 +07:00
|
|
|
__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
|
2005-10-31 06:03:00 +07:00
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|
|
EXPORT_SYMBOL(jiffies_64);
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|
2005-04-17 05:20:36 +07:00
|
|
|
/*
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|
|
|
* per-CPU timer vector definitions:
|
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|
|
*/
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|
#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
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|
#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
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#define TVN_SIZE (1 << TVN_BITS)
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#define TVR_SIZE (1 << TVR_BITS)
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|
#define TVN_MASK (TVN_SIZE - 1)
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|
|
#define TVR_MASK (TVR_SIZE - 1)
|
2012-10-08 20:49:03 +07:00
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|
|
#define MAX_TVAL ((unsigned long)((1ULL << (TVR_BITS + 4*TVN_BITS)) - 1))
|
2005-04-17 05:20:36 +07:00
|
|
|
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec {
|
2005-04-17 05:20:36 +07:00
|
|
|
struct list_head vec[TVN_SIZE];
|
2008-01-30 19:30:00 +07:00
|
|
|
};
|
2005-04-17 05:20:36 +07:00
|
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|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_root {
|
2005-04-17 05:20:36 +07:00
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|
|
struct list_head vec[TVR_SIZE];
|
2008-01-30 19:30:00 +07:00
|
|
|
};
|
2005-04-17 05:20:36 +07:00
|
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|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base {
|
2006-03-31 17:30:30 +07:00
|
|
|
spinlock_t lock;
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|
|
struct timer_list *running_timer;
|
2005-04-17 05:20:36 +07:00
|
|
|
unsigned long timer_jiffies;
|
2009-07-22 01:25:05 +07:00
|
|
|
unsigned long next_timer;
|
2012-05-26 05:08:58 +07:00
|
|
|
unsigned long active_timers;
|
2014-01-15 11:20:43 +07:00
|
|
|
unsigned long all_timers;
|
2014-06-22 06:29:13 +07:00
|
|
|
int cpu;
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_root tv1;
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|
|
struct tvec tv2;
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|
struct tvec tv3;
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|
struct tvec tv4;
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|
struct tvec tv5;
|
2007-05-08 14:27:44 +07:00
|
|
|
} ____cacheline_aligned;
|
2005-04-17 05:20:36 +07:00
|
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|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base boot_tvec_bases;
|
2006-03-31 17:30:30 +07:00
|
|
|
EXPORT_SYMBOL(boot_tvec_bases);
|
2008-01-30 19:30:00 +07:00
|
|
|
static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
|
2005-04-17 05:20:36 +07:00
|
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|
2007-05-08 14:27:44 +07:00
|
|
|
/* Functions below help us manage 'deferrable' flag */
|
2008-01-30 19:30:00 +07:00
|
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|
static inline unsigned int tbase_get_deferrable(struct tvec_base *base)
|
2007-05-08 14:27:44 +07:00
|
|
|
{
|
2012-08-09 01:10:25 +07:00
|
|
|
return ((unsigned int)(unsigned long)base & TIMER_DEFERRABLE);
|
2007-05-08 14:27:44 +07:00
|
|
|
}
|
|
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|
|
2012-08-09 01:10:28 +07:00
|
|
|
static inline unsigned int tbase_get_irqsafe(struct tvec_base *base)
|
|
|
|
{
|
|
|
|
return ((unsigned int)(unsigned long)base & TIMER_IRQSAFE);
|
|
|
|
}
|
|
|
|
|
2008-01-30 19:30:00 +07:00
|
|
|
static inline struct tvec_base *tbase_get_base(struct tvec_base *base)
|
2007-05-08 14:27:44 +07:00
|
|
|
{
|
2012-08-09 01:10:25 +07:00
|
|
|
return ((struct tvec_base *)((unsigned long)base & ~TIMER_FLAG_MASK));
|
2007-05-08 14:27:44 +07:00
|
|
|
}
|
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|
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|
|
static inline void
|
2008-01-30 19:30:00 +07:00
|
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|
timer_set_base(struct timer_list *timer, struct tvec_base *new_base)
|
2007-05-08 14:27:44 +07:00
|
|
|
{
|
2012-08-09 01:10:25 +07:00
|
|
|
unsigned long flags = (unsigned long)timer->base & TIMER_FLAG_MASK;
|
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|
timer->base = (struct tvec_base *)((unsigned long)(new_base) | flags);
|
2007-05-08 14:27:44 +07:00
|
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|
}
|
|
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|
2008-11-06 14:42:48 +07:00
|
|
|
static unsigned long round_jiffies_common(unsigned long j, int cpu,
|
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|
|
bool force_up)
|
2006-12-10 17:21:24 +07:00
|
|
|
{
|
|
|
|
int rem;
|
|
|
|
unsigned long original = j;
|
|
|
|
|
|
|
|
/*
|
|
|
|
* We don't want all cpus firing their timers at once hitting the
|
|
|
|
* same lock or cachelines, so we skew each extra cpu with an extra
|
|
|
|
* 3 jiffies. This 3 jiffies came originally from the mm/ code which
|
|
|
|
* already did this.
|
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|
|
* The skew is done by adding 3*cpunr, then round, then subtract this
|
|
|
|
* extra offset again.
|
|
|
|
*/
|
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|
j += cpu * 3;
|
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|
|
rem = j % HZ;
|
|
|
|
|
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|
|
/*
|
|
|
|
* If the target jiffie is just after a whole second (which can happen
|
|
|
|
* due to delays of the timer irq, long irq off times etc etc) then
|
|
|
|
* we should round down to the whole second, not up. Use 1/4th second
|
|
|
|
* as cutoff for this rounding as an extreme upper bound for this.
|
2008-11-06 14:42:48 +07:00
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|
* But never round down if @force_up is set.
|
2006-12-10 17:21:24 +07:00
|
|
|
*/
|
2008-11-06 14:42:48 +07:00
|
|
|
if (rem < HZ/4 && !force_up) /* round down */
|
2006-12-10 17:21:24 +07:00
|
|
|
j = j - rem;
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|
else /* round up */
|
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|
|
j = j - rem + HZ;
|
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|
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|
|
/* now that we have rounded, subtract the extra skew again */
|
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|
|
j -= cpu * 3;
|
|
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|
2013-05-22 01:43:50 +07:00
|
|
|
/*
|
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|
|
* Make sure j is still in the future. Otherwise return the
|
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|
|
* unmodified value.
|
|
|
|
*/
|
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|
|
return time_is_after_jiffies(j) ? j : original;
|
2006-12-10 17:21:24 +07:00
|
|
|
}
|
2008-11-06 14:42:48 +07:00
|
|
|
|
|
|
|
/**
|
|
|
|
* __round_jiffies - function to round jiffies to a full second
|
|
|
|
* @j: the time in (absolute) jiffies that should be rounded
|
|
|
|
* @cpu: the processor number on which the timeout will happen
|
|
|
|
*
|
|
|
|
* __round_jiffies() rounds an absolute time in the future (in jiffies)
|
|
|
|
* up or down to (approximately) full seconds. This is useful for timers
|
|
|
|
* for which the exact time they fire does not matter too much, as long as
|
|
|
|
* they fire approximately every X seconds.
|
|
|
|
*
|
|
|
|
* By rounding these timers to whole seconds, all such timers will fire
|
|
|
|
* at the same time, rather than at various times spread out. The goal
|
|
|
|
* of this is to have the CPU wake up less, which saves power.
|
|
|
|
*
|
|
|
|
* The exact rounding is skewed for each processor to avoid all
|
|
|
|
* processors firing at the exact same time, which could lead
|
|
|
|
* to lock contention or spurious cache line bouncing.
|
|
|
|
*
|
|
|
|
* The return value is the rounded version of the @j parameter.
|
|
|
|
*/
|
|
|
|
unsigned long __round_jiffies(unsigned long j, int cpu)
|
|
|
|
{
|
|
|
|
return round_jiffies_common(j, cpu, false);
|
|
|
|
}
|
2006-12-10 17:21:24 +07:00
|
|
|
EXPORT_SYMBOL_GPL(__round_jiffies);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* __round_jiffies_relative - function to round jiffies to a full second
|
|
|
|
* @j: the time in (relative) jiffies that should be rounded
|
|
|
|
* @cpu: the processor number on which the timeout will happen
|
|
|
|
*
|
2007-02-10 16:45:59 +07:00
|
|
|
* __round_jiffies_relative() rounds a time delta in the future (in jiffies)
|
2006-12-10 17:21:24 +07:00
|
|
|
* up or down to (approximately) full seconds. This is useful for timers
|
|
|
|
* for which the exact time they fire does not matter too much, as long as
|
|
|
|
* they fire approximately every X seconds.
|
|
|
|
*
|
|
|
|
* By rounding these timers to whole seconds, all such timers will fire
|
|
|
|
* at the same time, rather than at various times spread out. The goal
|
|
|
|
* of this is to have the CPU wake up less, which saves power.
|
|
|
|
*
|
|
|
|
* The exact rounding is skewed for each processor to avoid all
|
|
|
|
* processors firing at the exact same time, which could lead
|
|
|
|
* to lock contention or spurious cache line bouncing.
|
|
|
|
*
|
2007-02-10 16:45:59 +07:00
|
|
|
* The return value is the rounded version of the @j parameter.
|
2006-12-10 17:21:24 +07:00
|
|
|
*/
|
|
|
|
unsigned long __round_jiffies_relative(unsigned long j, int cpu)
|
|
|
|
{
|
2008-11-06 14:42:48 +07:00
|
|
|
unsigned long j0 = jiffies;
|
|
|
|
|
|
|
|
/* Use j0 because jiffies might change while we run */
|
|
|
|
return round_jiffies_common(j + j0, cpu, false) - j0;
|
2006-12-10 17:21:24 +07:00
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(__round_jiffies_relative);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* round_jiffies - function to round jiffies to a full second
|
|
|
|
* @j: the time in (absolute) jiffies that should be rounded
|
|
|
|
*
|
2007-02-10 16:45:59 +07:00
|
|
|
* round_jiffies() rounds an absolute time in the future (in jiffies)
|
2006-12-10 17:21:24 +07:00
|
|
|
* up or down to (approximately) full seconds. This is useful for timers
|
|
|
|
* for which the exact time they fire does not matter too much, as long as
|
|
|
|
* they fire approximately every X seconds.
|
|
|
|
*
|
|
|
|
* By rounding these timers to whole seconds, all such timers will fire
|
|
|
|
* at the same time, rather than at various times spread out. The goal
|
|
|
|
* of this is to have the CPU wake up less, which saves power.
|
|
|
|
*
|
2007-02-10 16:45:59 +07:00
|
|
|
* The return value is the rounded version of the @j parameter.
|
2006-12-10 17:21:24 +07:00
|
|
|
*/
|
|
|
|
unsigned long round_jiffies(unsigned long j)
|
|
|
|
{
|
2008-11-06 14:42:48 +07:00
|
|
|
return round_jiffies_common(j, raw_smp_processor_id(), false);
|
2006-12-10 17:21:24 +07:00
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(round_jiffies);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* round_jiffies_relative - function to round jiffies to a full second
|
|
|
|
* @j: the time in (relative) jiffies that should be rounded
|
|
|
|
*
|
2007-02-10 16:45:59 +07:00
|
|
|
* round_jiffies_relative() rounds a time delta in the future (in jiffies)
|
2006-12-10 17:21:24 +07:00
|
|
|
* up or down to (approximately) full seconds. This is useful for timers
|
|
|
|
* for which the exact time they fire does not matter too much, as long as
|
|
|
|
* they fire approximately every X seconds.
|
|
|
|
*
|
|
|
|
* By rounding these timers to whole seconds, all such timers will fire
|
|
|
|
* at the same time, rather than at various times spread out. The goal
|
|
|
|
* of this is to have the CPU wake up less, which saves power.
|
|
|
|
*
|
2007-02-10 16:45:59 +07:00
|
|
|
* The return value is the rounded version of the @j parameter.
|
2006-12-10 17:21:24 +07:00
|
|
|
*/
|
|
|
|
unsigned long round_jiffies_relative(unsigned long j)
|
|
|
|
{
|
|
|
|
return __round_jiffies_relative(j, raw_smp_processor_id());
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(round_jiffies_relative);
|
|
|
|
|
2008-11-06 14:42:48 +07:00
|
|
|
/**
|
|
|
|
* __round_jiffies_up - function to round jiffies up to a full second
|
|
|
|
* @j: the time in (absolute) jiffies that should be rounded
|
|
|
|
* @cpu: the processor number on which the timeout will happen
|
|
|
|
*
|
|
|
|
* This is the same as __round_jiffies() except that it will never
|
|
|
|
* round down. This is useful for timeouts for which the exact time
|
|
|
|
* of firing does not matter too much, as long as they don't fire too
|
|
|
|
* early.
|
|
|
|
*/
|
|
|
|
unsigned long __round_jiffies_up(unsigned long j, int cpu)
|
|
|
|
{
|
|
|
|
return round_jiffies_common(j, cpu, true);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(__round_jiffies_up);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* __round_jiffies_up_relative - function to round jiffies up to a full second
|
|
|
|
* @j: the time in (relative) jiffies that should be rounded
|
|
|
|
* @cpu: the processor number on which the timeout will happen
|
|
|
|
*
|
|
|
|
* This is the same as __round_jiffies_relative() except that it will never
|
|
|
|
* round down. This is useful for timeouts for which the exact time
|
|
|
|
* of firing does not matter too much, as long as they don't fire too
|
|
|
|
* early.
|
|
|
|
*/
|
|
|
|
unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
|
|
|
|
{
|
|
|
|
unsigned long j0 = jiffies;
|
|
|
|
|
|
|
|
/* Use j0 because jiffies might change while we run */
|
|
|
|
return round_jiffies_common(j + j0, cpu, true) - j0;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* round_jiffies_up - function to round jiffies up to a full second
|
|
|
|
* @j: the time in (absolute) jiffies that should be rounded
|
|
|
|
*
|
|
|
|
* This is the same as round_jiffies() except that it will never
|
|
|
|
* round down. This is useful for timeouts for which the exact time
|
|
|
|
* of firing does not matter too much, as long as they don't fire too
|
|
|
|
* early.
|
|
|
|
*/
|
|
|
|
unsigned long round_jiffies_up(unsigned long j)
|
|
|
|
{
|
|
|
|
return round_jiffies_common(j, raw_smp_processor_id(), true);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(round_jiffies_up);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* round_jiffies_up_relative - function to round jiffies up to a full second
|
|
|
|
* @j: the time in (relative) jiffies that should be rounded
|
|
|
|
*
|
|
|
|
* This is the same as round_jiffies_relative() except that it will never
|
|
|
|
* round down. This is useful for timeouts for which the exact time
|
|
|
|
* of firing does not matter too much, as long as they don't fire too
|
|
|
|
* early.
|
|
|
|
*/
|
|
|
|
unsigned long round_jiffies_up_relative(unsigned long j)
|
|
|
|
{
|
|
|
|
return __round_jiffies_up_relative(j, raw_smp_processor_id());
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
|
|
|
|
|
2010-03-12 05:04:36 +07:00
|
|
|
/**
|
|
|
|
* set_timer_slack - set the allowed slack for a timer
|
2010-08-10 06:32:50 +07:00
|
|
|
* @timer: the timer to be modified
|
2010-03-12 05:04:36 +07:00
|
|
|
* @slack_hz: the amount of time (in jiffies) allowed for rounding
|
|
|
|
*
|
|
|
|
* Set the amount of time, in jiffies, that a certain timer has
|
|
|
|
* in terms of slack. By setting this value, the timer subsystem
|
|
|
|
* will schedule the actual timer somewhere between
|
|
|
|
* the time mod_timer() asks for, and that time plus the slack.
|
|
|
|
*
|
|
|
|
* By setting the slack to -1, a percentage of the delay is used
|
|
|
|
* instead.
|
|
|
|
*/
|
|
|
|
void set_timer_slack(struct timer_list *timer, int slack_hz)
|
|
|
|
{
|
|
|
|
timer->slack = slack_hz;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(set_timer_slack);
|
|
|
|
|
2013-12-16 20:57:10 +07:00
|
|
|
/*
|
|
|
|
* If the list is empty, catch up ->timer_jiffies to the current time.
|
|
|
|
* The caller must hold the tvec_base lock. Returns true if the list
|
|
|
|
* was empty and therefore ->timer_jiffies was updated.
|
|
|
|
*/
|
|
|
|
static bool catchup_timer_jiffies(struct tvec_base *base)
|
|
|
|
{
|
|
|
|
if (!base->all_timers) {
|
|
|
|
base->timer_jiffies = jiffies;
|
|
|
|
return true;
|
|
|
|
}
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
|
2012-05-26 05:08:57 +07:00
|
|
|
static void
|
|
|
|
__internal_add_timer(struct tvec_base *base, struct timer_list *timer)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
|
|
|
unsigned long expires = timer->expires;
|
|
|
|
unsigned long idx = expires - base->timer_jiffies;
|
|
|
|
struct list_head *vec;
|
|
|
|
|
|
|
|
if (idx < TVR_SIZE) {
|
|
|
|
int i = expires & TVR_MASK;
|
|
|
|
vec = base->tv1.vec + i;
|
|
|
|
} else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
|
|
|
|
int i = (expires >> TVR_BITS) & TVN_MASK;
|
|
|
|
vec = base->tv2.vec + i;
|
|
|
|
} else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
|
|
|
|
int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
|
|
|
|
vec = base->tv3.vec + i;
|
|
|
|
} else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
|
|
|
|
int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
|
|
|
|
vec = base->tv4.vec + i;
|
|
|
|
} else if ((signed long) idx < 0) {
|
|
|
|
/*
|
|
|
|
* Can happen if you add a timer with expires == jiffies,
|
|
|
|
* or you set a timer to go off in the past
|
|
|
|
*/
|
|
|
|
vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
|
|
|
|
} else {
|
|
|
|
int i;
|
2012-10-08 20:49:03 +07:00
|
|
|
/* If the timeout is larger than MAX_TVAL (on 64-bit
|
|
|
|
* architectures or with CONFIG_BASE_SMALL=1) then we
|
|
|
|
* use the maximum timeout.
|
2005-04-17 05:20:36 +07:00
|
|
|
*/
|
2012-10-08 20:49:03 +07:00
|
|
|
if (idx > MAX_TVAL) {
|
|
|
|
idx = MAX_TVAL;
|
2005-04-17 05:20:36 +07:00
|
|
|
expires = idx + base->timer_jiffies;
|
|
|
|
}
|
|
|
|
i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
|
|
|
|
vec = base->tv5.vec + i;
|
|
|
|
}
|
|
|
|
/*
|
|
|
|
* Timers are FIFO:
|
|
|
|
*/
|
|
|
|
list_add_tail(&timer->entry, vec);
|
|
|
|
}
|
|
|
|
|
2012-05-26 05:08:57 +07:00
|
|
|
static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
|
|
|
|
{
|
2013-12-17 01:41:50 +07:00
|
|
|
(void)catchup_timer_jiffies(base);
|
2012-05-26 05:08:57 +07:00
|
|
|
__internal_add_timer(base, timer);
|
|
|
|
/*
|
2012-05-26 05:08:58 +07:00
|
|
|
* Update base->active_timers and base->next_timer
|
2012-05-26 05:08:57 +07:00
|
|
|
*/
|
2012-05-26 05:08:58 +07:00
|
|
|
if (!tbase_get_deferrable(timer->base)) {
|
2014-01-16 07:19:27 +07:00
|
|
|
if (!base->active_timers++ ||
|
|
|
|
time_before(timer->expires, base->next_timer))
|
2012-05-26 05:08:58 +07:00
|
|
|
base->next_timer = timer->expires;
|
|
|
|
}
|
2014-01-15 11:20:43 +07:00
|
|
|
base->all_timers++;
|
2014-06-22 06:29:14 +07:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Check whether the other CPU is in dynticks mode and needs
|
|
|
|
* to be triggered to reevaluate the timer wheel.
|
|
|
|
* We are protected against the other CPU fiddling
|
|
|
|
* with the timer by holding the timer base lock. This also
|
|
|
|
* makes sure that a CPU on the way to stop its tick can not
|
|
|
|
* evaluate the timer wheel.
|
|
|
|
*
|
|
|
|
* Spare the IPI for deferrable timers on idle targets though.
|
|
|
|
* The next busy ticks will take care of it. Except full dynticks
|
|
|
|
* require special care against races with idle_cpu(), lets deal
|
|
|
|
* with that later.
|
|
|
|
*/
|
|
|
|
if (!tbase_get_deferrable(base) || tick_nohz_full_cpu(base->cpu))
|
|
|
|
wake_up_nohz_cpu(base->cpu);
|
2012-05-26 05:08:57 +07:00
|
|
|
}
|
|
|
|
|
[PATCH] Add debugging feature /proc/timer_stat
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.
Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec
[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 16:28:13 +07:00
|
|
|
#ifdef CONFIG_TIMER_STATS
|
|
|
|
void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
|
|
|
|
{
|
|
|
|
if (timer->start_site)
|
|
|
|
return;
|
|
|
|
|
|
|
|
timer->start_site = addr;
|
|
|
|
memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
|
|
|
|
timer->start_pid = current->pid;
|
|
|
|
}
|
2007-07-16 13:40:30 +07:00
|
|
|
|
|
|
|
static void timer_stats_account_timer(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
unsigned int flag = 0;
|
|
|
|
|
2009-06-23 22:38:15 +07:00
|
|
|
if (likely(!timer->start_site))
|
|
|
|
return;
|
2007-07-16 13:40:30 +07:00
|
|
|
if (unlikely(tbase_get_deferrable(timer->base)))
|
|
|
|
flag |= TIMER_STATS_FLAG_DEFERRABLE;
|
|
|
|
|
|
|
|
timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
|
|
|
|
timer->function, timer->start_comm, flag);
|
|
|
|
}
|
|
|
|
|
|
|
|
#else
|
|
|
|
static void timer_stats_account_timer(struct timer_list *timer) {}
|
[PATCH] Add debugging feature /proc/timer_stat
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.
Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec
[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 16:28:13 +07:00
|
|
|
#endif
|
|
|
|
|
2008-04-30 14:55:03 +07:00
|
|
|
#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
|
|
|
|
|
|
|
|
static struct debug_obj_descr timer_debug_descr;
|
|
|
|
|
2011-03-07 15:58:33 +07:00
|
|
|
static void *timer_debug_hint(void *addr)
|
|
|
|
{
|
|
|
|
return ((struct timer_list *) addr)->function;
|
|
|
|
}
|
|
|
|
|
2008-04-30 14:55:03 +07:00
|
|
|
/*
|
|
|
|
* fixup_init is called when:
|
|
|
|
* - an active object is initialized
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
*/
|
2008-04-30 14:55:03 +07:00
|
|
|
static int timer_fixup_init(void *addr, enum debug_obj_state state)
|
|
|
|
{
|
|
|
|
struct timer_list *timer = addr;
|
|
|
|
|
|
|
|
switch (state) {
|
|
|
|
case ODEBUG_STATE_ACTIVE:
|
|
|
|
del_timer_sync(timer);
|
|
|
|
debug_object_init(timer, &timer_debug_descr);
|
|
|
|
return 1;
|
|
|
|
default:
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2011-11-08 10:48:26 +07:00
|
|
|
/* Stub timer callback for improperly used timers. */
|
|
|
|
static void stub_timer(unsigned long data)
|
|
|
|
{
|
|
|
|
WARN_ON(1);
|
|
|
|
}
|
|
|
|
|
2008-04-30 14:55:03 +07:00
|
|
|
/*
|
|
|
|
* fixup_activate is called when:
|
|
|
|
* - an active object is activated
|
|
|
|
* - an unknown object is activated (might be a statically initialized object)
|
|
|
|
*/
|
|
|
|
static int timer_fixup_activate(void *addr, enum debug_obj_state state)
|
|
|
|
{
|
|
|
|
struct timer_list *timer = addr;
|
|
|
|
|
|
|
|
switch (state) {
|
|
|
|
|
|
|
|
case ODEBUG_STATE_NOTAVAILABLE:
|
|
|
|
/*
|
|
|
|
* This is not really a fixup. The timer was
|
|
|
|
* statically initialized. We just make sure that it
|
|
|
|
* is tracked in the object tracker.
|
|
|
|
*/
|
|
|
|
if (timer->entry.next == NULL &&
|
|
|
|
timer->entry.prev == TIMER_ENTRY_STATIC) {
|
|
|
|
debug_object_init(timer, &timer_debug_descr);
|
|
|
|
debug_object_activate(timer, &timer_debug_descr);
|
|
|
|
return 0;
|
|
|
|
} else {
|
2011-11-08 10:48:26 +07:00
|
|
|
setup_timer(timer, stub_timer, 0);
|
|
|
|
return 1;
|
2008-04-30 14:55:03 +07:00
|
|
|
}
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
case ODEBUG_STATE_ACTIVE:
|
|
|
|
WARN_ON(1);
|
|
|
|
|
|
|
|
default:
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* fixup_free is called when:
|
|
|
|
* - an active object is freed
|
|
|
|
*/
|
|
|
|
static int timer_fixup_free(void *addr, enum debug_obj_state state)
|
|
|
|
{
|
|
|
|
struct timer_list *timer = addr;
|
|
|
|
|
|
|
|
switch (state) {
|
|
|
|
case ODEBUG_STATE_ACTIVE:
|
|
|
|
del_timer_sync(timer);
|
|
|
|
debug_object_free(timer, &timer_debug_descr);
|
|
|
|
return 1;
|
|
|
|
default:
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2011-11-08 10:48:28 +07:00
|
|
|
/*
|
|
|
|
* fixup_assert_init is called when:
|
|
|
|
* - an untracked/uninit-ed object is found
|
|
|
|
*/
|
|
|
|
static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)
|
|
|
|
{
|
|
|
|
struct timer_list *timer = addr;
|
|
|
|
|
|
|
|
switch (state) {
|
|
|
|
case ODEBUG_STATE_NOTAVAILABLE:
|
|
|
|
if (timer->entry.prev == TIMER_ENTRY_STATIC) {
|
|
|
|
/*
|
|
|
|
* This is not really a fixup. The timer was
|
|
|
|
* statically initialized. We just make sure that it
|
|
|
|
* is tracked in the object tracker.
|
|
|
|
*/
|
|
|
|
debug_object_init(timer, &timer_debug_descr);
|
|
|
|
return 0;
|
|
|
|
} else {
|
|
|
|
setup_timer(timer, stub_timer, 0);
|
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
default:
|
|
|
|
return 0;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2008-04-30 14:55:03 +07:00
|
|
|
static struct debug_obj_descr timer_debug_descr = {
|
2011-11-08 10:48:28 +07:00
|
|
|
.name = "timer_list",
|
|
|
|
.debug_hint = timer_debug_hint,
|
|
|
|
.fixup_init = timer_fixup_init,
|
|
|
|
.fixup_activate = timer_fixup_activate,
|
|
|
|
.fixup_free = timer_fixup_free,
|
|
|
|
.fixup_assert_init = timer_fixup_assert_init,
|
2008-04-30 14:55:03 +07:00
|
|
|
};
|
|
|
|
|
|
|
|
static inline void debug_timer_init(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_object_init(timer, &timer_debug_descr);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void debug_timer_activate(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_object_activate(timer, &timer_debug_descr);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void debug_timer_deactivate(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_object_deactivate(timer, &timer_debug_descr);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void debug_timer_free(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_object_free(timer, &timer_debug_descr);
|
|
|
|
}
|
|
|
|
|
2011-11-08 10:48:28 +07:00
|
|
|
static inline void debug_timer_assert_init(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_object_assert_init(timer, &timer_debug_descr);
|
|
|
|
}
|
|
|
|
|
2012-08-09 01:10:27 +07:00
|
|
|
static void do_init_timer(struct timer_list *timer, unsigned int flags,
|
|
|
|
const char *name, struct lock_class_key *key);
|
2008-04-30 14:55:03 +07:00
|
|
|
|
2012-08-09 01:10:27 +07:00
|
|
|
void init_timer_on_stack_key(struct timer_list *timer, unsigned int flags,
|
|
|
|
const char *name, struct lock_class_key *key)
|
2008-04-30 14:55:03 +07:00
|
|
|
{
|
|
|
|
debug_object_init_on_stack(timer, &timer_debug_descr);
|
2012-08-09 01:10:27 +07:00
|
|
|
do_init_timer(timer, flags, name, key);
|
2008-04-30 14:55:03 +07:00
|
|
|
}
|
2009-01-29 22:03:20 +07:00
|
|
|
EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
|
2008-04-30 14:55:03 +07:00
|
|
|
|
|
|
|
void destroy_timer_on_stack(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_object_free(timer, &timer_debug_descr);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
|
|
|
|
|
|
|
|
#else
|
|
|
|
static inline void debug_timer_init(struct timer_list *timer) { }
|
|
|
|
static inline void debug_timer_activate(struct timer_list *timer) { }
|
|
|
|
static inline void debug_timer_deactivate(struct timer_list *timer) { }
|
2011-11-08 10:48:28 +07:00
|
|
|
static inline void debug_timer_assert_init(struct timer_list *timer) { }
|
2008-04-30 14:55:03 +07:00
|
|
|
#endif
|
|
|
|
|
2009-08-10 09:48:59 +07:00
|
|
|
static inline void debug_init(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_timer_init(timer);
|
|
|
|
trace_timer_init(timer);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void
|
|
|
|
debug_activate(struct timer_list *timer, unsigned long expires)
|
|
|
|
{
|
|
|
|
debug_timer_activate(timer);
|
|
|
|
trace_timer_start(timer, expires);
|
|
|
|
}
|
|
|
|
|
|
|
|
static inline void debug_deactivate(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_timer_deactivate(timer);
|
|
|
|
trace_timer_cancel(timer);
|
|
|
|
}
|
|
|
|
|
2011-11-08 10:48:28 +07:00
|
|
|
static inline void debug_assert_init(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
debug_timer_assert_init(timer);
|
|
|
|
}
|
|
|
|
|
2012-08-09 01:10:27 +07:00
|
|
|
static void do_init_timer(struct timer_list *timer, unsigned int flags,
|
|
|
|
const char *name, struct lock_class_key *key)
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
{
|
2012-08-09 01:10:27 +07:00
|
|
|
struct tvec_base *base = __raw_get_cpu_var(tvec_bases);
|
|
|
|
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
timer->entry.next = NULL;
|
2012-08-09 01:10:27 +07:00
|
|
|
timer->base = (void *)((unsigned long)base | flags);
|
2010-03-12 05:04:36 +07:00
|
|
|
timer->slack = -1;
|
[PATCH] Add debugging feature /proc/timer_stat
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.
Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec
[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 16:28:13 +07:00
|
|
|
#ifdef CONFIG_TIMER_STATS
|
|
|
|
timer->start_site = NULL;
|
|
|
|
timer->start_pid = -1;
|
|
|
|
memset(timer->start_comm, 0, TASK_COMM_LEN);
|
|
|
|
#endif
|
2009-01-29 22:03:20 +07:00
|
|
|
lockdep_init_map(&timer->lockdep_map, name, key, 0);
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
}
|
2008-04-30 14:55:03 +07:00
|
|
|
|
|
|
|
/**
|
2009-04-02 07:47:23 +07:00
|
|
|
* init_timer_key - initialize a timer
|
2008-04-30 14:55:03 +07:00
|
|
|
* @timer: the timer to be initialized
|
2012-08-09 01:10:27 +07:00
|
|
|
* @flags: timer flags
|
2009-04-02 07:47:23 +07:00
|
|
|
* @name: name of the timer
|
|
|
|
* @key: lockdep class key of the fake lock used for tracking timer
|
|
|
|
* sync lock dependencies
|
2008-04-30 14:55:03 +07:00
|
|
|
*
|
2009-04-02 07:47:23 +07:00
|
|
|
* init_timer_key() must be done to a timer prior calling *any* of the
|
2008-04-30 14:55:03 +07:00
|
|
|
* other timer functions.
|
|
|
|
*/
|
2012-08-09 01:10:27 +07:00
|
|
|
void init_timer_key(struct timer_list *timer, unsigned int flags,
|
|
|
|
const char *name, struct lock_class_key *key)
|
2008-04-30 14:55:03 +07:00
|
|
|
{
|
2009-08-10 09:48:59 +07:00
|
|
|
debug_init(timer);
|
2012-08-09 01:10:27 +07:00
|
|
|
do_init_timer(timer, flags, name, key);
|
2008-04-30 14:55:03 +07:00
|
|
|
}
|
2009-01-29 22:03:20 +07:00
|
|
|
EXPORT_SYMBOL(init_timer_key);
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
|
2012-05-26 05:08:57 +07:00
|
|
|
static inline void detach_timer(struct timer_list *timer, bool clear_pending)
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
{
|
|
|
|
struct list_head *entry = &timer->entry;
|
|
|
|
|
2009-08-10 09:48:59 +07:00
|
|
|
debug_deactivate(timer);
|
2008-04-30 14:55:03 +07:00
|
|
|
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
__list_del(entry->prev, entry->next);
|
|
|
|
if (clear_pending)
|
|
|
|
entry->next = NULL;
|
|
|
|
entry->prev = LIST_POISON2;
|
|
|
|
}
|
|
|
|
|
2012-05-26 05:08:58 +07:00
|
|
|
static inline void
|
|
|
|
detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
|
|
|
|
{
|
|
|
|
detach_timer(timer, true);
|
|
|
|
if (!tbase_get_deferrable(timer->base))
|
2012-08-09 01:10:25 +07:00
|
|
|
base->active_timers--;
|
2014-01-15 11:20:43 +07:00
|
|
|
base->all_timers--;
|
2013-12-17 01:32:01 +07:00
|
|
|
(void)catchup_timer_jiffies(base);
|
2012-05-26 05:08:58 +07:00
|
|
|
}
|
|
|
|
|
2012-05-26 05:08:57 +07:00
|
|
|
static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
|
|
|
|
bool clear_pending)
|
|
|
|
{
|
|
|
|
if (!timer_pending(timer))
|
|
|
|
return 0;
|
|
|
|
|
|
|
|
detach_timer(timer, clear_pending);
|
2012-05-26 05:08:58 +07:00
|
|
|
if (!tbase_get_deferrable(timer->base)) {
|
2012-08-09 01:10:25 +07:00
|
|
|
base->active_timers--;
|
2012-05-26 05:08:58 +07:00
|
|
|
if (timer->expires == base->next_timer)
|
|
|
|
base->next_timer = base->timer_jiffies;
|
|
|
|
}
|
2014-01-15 11:20:43 +07:00
|
|
|
base->all_timers--;
|
2013-12-17 01:32:01 +07:00
|
|
|
(void)catchup_timer_jiffies(base);
|
2012-05-26 05:08:57 +07:00
|
|
|
return 1;
|
|
|
|
}
|
|
|
|
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
/*
|
2006-03-31 17:30:30 +07:00
|
|
|
* We are using hashed locking: holding per_cpu(tvec_bases).lock
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
* means that all timers which are tied to this base via timer->base are
|
|
|
|
* locked, and the base itself is locked too.
|
|
|
|
*
|
|
|
|
* So __run_timers/migrate_timers can safely modify all timers which could
|
|
|
|
* be found on ->tvX lists.
|
|
|
|
*
|
|
|
|
* When the timer's base is locked, and the timer removed from list, it is
|
|
|
|
* possible to set timer->base = NULL and drop the lock: the timer remains
|
|
|
|
* locked.
|
|
|
|
*/
|
2008-01-30 19:30:00 +07:00
|
|
|
static struct tvec_base *lock_timer_base(struct timer_list *timer,
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
unsigned long *flags)
|
2006-09-29 15:59:36 +07:00
|
|
|
__acquires(timer->base->lock)
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
{
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base *base;
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
|
|
|
|
for (;;) {
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base *prelock_base = timer->base;
|
2007-05-08 14:27:44 +07:00
|
|
|
base = tbase_get_base(prelock_base);
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
if (likely(base != NULL)) {
|
|
|
|
spin_lock_irqsave(&base->lock, *flags);
|
2007-05-08 14:27:44 +07:00
|
|
|
if (likely(prelock_base == timer->base))
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
return base;
|
|
|
|
/* The timer has migrated to another CPU */
|
|
|
|
spin_unlock_irqrestore(&base->lock, *flags);
|
|
|
|
}
|
|
|
|
cpu_relax();
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2009-02-18 18:23:29 +07:00
|
|
|
static inline int
|
2009-04-16 13:43:26 +07:00
|
|
|
__mod_timer(struct timer_list *timer, unsigned long expires,
|
|
|
|
bool pending_only, int pinned)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base *base, *new_base;
|
2005-04-17 05:20:36 +07:00
|
|
|
unsigned long flags;
|
2009-04-16 13:46:41 +07:00
|
|
|
int ret = 0 , cpu;
|
2005-04-17 05:20:36 +07:00
|
|
|
|
[PATCH] Add debugging feature /proc/timer_stat
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.
Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec
[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 16:28:13 +07:00
|
|
|
timer_stats_timer_set_start_info(timer);
|
2005-04-17 05:20:36 +07:00
|
|
|
BUG_ON(!timer->function);
|
|
|
|
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
base = lock_timer_base(timer, &flags);
|
|
|
|
|
2012-05-26 05:08:57 +07:00
|
|
|
ret = detach_if_pending(timer, base, false);
|
|
|
|
if (!ret && pending_only)
|
|
|
|
goto out_unlock;
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
|
2009-08-10 09:48:59 +07:00
|
|
|
debug_activate(timer, expires);
|
2008-04-30 14:55:03 +07:00
|
|
|
|
2014-03-18 17:56:07 +07:00
|
|
|
cpu = get_nohz_timer_target(pinned);
|
2009-04-16 13:46:41 +07:00
|
|
|
new_base = per_cpu(tvec_bases, cpu);
|
|
|
|
|
2006-03-31 17:30:30 +07:00
|
|
|
if (base != new_base) {
|
2005-04-17 05:20:36 +07:00
|
|
|
/*
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
* We are trying to schedule the timer on the local CPU.
|
|
|
|
* However we can't change timer's base while it is running,
|
|
|
|
* otherwise del_timer_sync() can't detect that the timer's
|
|
|
|
* handler yet has not finished. This also guarantees that
|
|
|
|
* the timer is serialized wrt itself.
|
2005-04-17 05:20:36 +07:00
|
|
|
*/
|
2006-03-31 17:30:31 +07:00
|
|
|
if (likely(base->running_timer != timer)) {
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
/* See the comment in lock_timer_base() */
|
2007-05-08 14:27:44 +07:00
|
|
|
timer_set_base(timer, NULL);
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
spin_unlock(&base->lock);
|
2006-03-31 17:30:31 +07:00
|
|
|
base = new_base;
|
|
|
|
spin_lock(&base->lock);
|
2007-05-08 14:27:44 +07:00
|
|
|
timer_set_base(timer, base);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
timer->expires = expires;
|
2006-03-31 17:30:31 +07:00
|
|
|
internal_add_timer(base, timer);
|
2009-02-18 18:23:29 +07:00
|
|
|
|
|
|
|
out_unlock:
|
2006-03-31 17:30:31 +07:00
|
|
|
spin_unlock_irqrestore(&base->lock, flags);
|
2005-04-17 05:20:36 +07:00
|
|
|
|
|
|
|
return ret;
|
|
|
|
}
|
|
|
|
|
2006-09-29 15:59:46 +07:00
|
|
|
/**
|
2009-02-18 18:23:29 +07:00
|
|
|
* mod_timer_pending - modify a pending timer's timeout
|
|
|
|
* @timer: the pending timer to be modified
|
|
|
|
* @expires: new timeout in jiffies
|
2005-04-17 05:20:36 +07:00
|
|
|
*
|
2009-02-18 18:23:29 +07:00
|
|
|
* mod_timer_pending() is the same for pending timers as mod_timer(),
|
|
|
|
* but will not re-activate and modify already deleted timers.
|
|
|
|
*
|
|
|
|
* It is useful for unserialized use of timers.
|
2005-04-17 05:20:36 +07:00
|
|
|
*/
|
2009-02-18 18:23:29 +07:00
|
|
|
int mod_timer_pending(struct timer_list *timer, unsigned long expires)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
2009-04-16 13:43:26 +07:00
|
|
|
return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
2009-02-18 18:23:29 +07:00
|
|
|
EXPORT_SYMBOL(mod_timer_pending);
|
2005-04-17 05:20:36 +07:00
|
|
|
|
2010-03-12 05:04:36 +07:00
|
|
|
/*
|
|
|
|
* Decide where to put the timer while taking the slack into account
|
|
|
|
*
|
|
|
|
* Algorithm:
|
|
|
|
* 1) calculate the maximum (absolute) time
|
|
|
|
* 2) calculate the highest bit where the expires and new max are different
|
|
|
|
* 3) use this bit to make a mask
|
|
|
|
* 4) use the bitmask to round down the maximum time, so that all last
|
|
|
|
* bits are zeros
|
|
|
|
*/
|
|
|
|
static inline
|
|
|
|
unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
|
|
|
|
{
|
|
|
|
unsigned long expires_limit, mask;
|
|
|
|
int bit;
|
|
|
|
|
2010-05-26 01:43:30 +07:00
|
|
|
if (timer->slack >= 0) {
|
2010-05-24 06:16:24 +07:00
|
|
|
expires_limit = expires + timer->slack;
|
2010-05-26 01:43:30 +07:00
|
|
|
} else {
|
2011-05-21 17:58:28 +07:00
|
|
|
long delta = expires - jiffies;
|
|
|
|
|
|
|
|
if (delta < 256)
|
|
|
|
return expires;
|
2010-03-12 05:04:36 +07:00
|
|
|
|
2011-05-21 17:58:28 +07:00
|
|
|
expires_limit = expires + delta / 256;
|
2010-05-26 01:43:30 +07:00
|
|
|
}
|
2010-03-12 05:04:36 +07:00
|
|
|
mask = expires ^ expires_limit;
|
|
|
|
if (mask == 0)
|
|
|
|
return expires;
|
|
|
|
|
|
|
|
bit = find_last_bit(&mask, BITS_PER_LONG);
|
|
|
|
|
2014-04-18 22:23:11 +07:00
|
|
|
mask = (1UL << bit) - 1;
|
2010-03-12 05:04:36 +07:00
|
|
|
|
|
|
|
expires_limit = expires_limit & ~(mask);
|
|
|
|
|
|
|
|
return expires_limit;
|
|
|
|
}
|
|
|
|
|
2006-09-29 15:59:46 +07:00
|
|
|
/**
|
2005-04-17 05:20:36 +07:00
|
|
|
* mod_timer - modify a timer's timeout
|
|
|
|
* @timer: the timer to be modified
|
2006-09-29 15:59:46 +07:00
|
|
|
* @expires: new timeout in jiffies
|
2005-04-17 05:20:36 +07:00
|
|
|
*
|
2007-02-10 16:45:59 +07:00
|
|
|
* mod_timer() is a more efficient way to update the expire field of an
|
2005-04-17 05:20:36 +07:00
|
|
|
* active timer (if the timer is inactive it will be activated)
|
|
|
|
*
|
|
|
|
* mod_timer(timer, expires) is equivalent to:
|
|
|
|
*
|
|
|
|
* del_timer(timer); timer->expires = expires; add_timer(timer);
|
|
|
|
*
|
|
|
|
* Note that if there are multiple unserialized concurrent users of the
|
|
|
|
* same timer, then mod_timer() is the only safe way to modify the timeout,
|
|
|
|
* since add_timer() cannot modify an already running timer.
|
|
|
|
*
|
|
|
|
* The function returns whether it has modified a pending timer or not.
|
|
|
|
* (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
|
|
|
|
* active timer returns 1.)
|
|
|
|
*/
|
|
|
|
int mod_timer(struct timer_list *timer, unsigned long expires)
|
|
|
|
{
|
2011-05-21 17:58:28 +07:00
|
|
|
expires = apply_slack(timer, expires);
|
|
|
|
|
2005-04-17 05:20:36 +07:00
|
|
|
/*
|
|
|
|
* This is a common optimization triggered by the
|
|
|
|
* networking code - if the timer is re-modified
|
|
|
|
* to be the same thing then just return:
|
|
|
|
*/
|
2009-07-19 03:46:02 +07:00
|
|
|
if (timer_pending(timer) && timer->expires == expires)
|
2005-04-17 05:20:36 +07:00
|
|
|
return 1;
|
|
|
|
|
2009-04-16 13:43:26 +07:00
|
|
|
return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(mod_timer);
|
|
|
|
|
2009-04-16 13:43:26 +07:00
|
|
|
/**
|
|
|
|
* mod_timer_pinned - modify a timer's timeout
|
|
|
|
* @timer: the timer to be modified
|
|
|
|
* @expires: new timeout in jiffies
|
|
|
|
*
|
|
|
|
* mod_timer_pinned() is a way to update the expire field of an
|
|
|
|
* active timer (if the timer is inactive it will be activated)
|
2012-04-27 00:52:27 +07:00
|
|
|
* and to ensure that the timer is scheduled on the current CPU.
|
|
|
|
*
|
|
|
|
* Note that this does not prevent the timer from being migrated
|
|
|
|
* when the current CPU goes offline. If this is a problem for
|
|
|
|
* you, use CPU-hotplug notifiers to handle it correctly, for
|
|
|
|
* example, cancelling the timer when the corresponding CPU goes
|
|
|
|
* offline.
|
2009-04-16 13:43:26 +07:00
|
|
|
*
|
|
|
|
* mod_timer_pinned(timer, expires) is equivalent to:
|
|
|
|
*
|
|
|
|
* del_timer(timer); timer->expires = expires; add_timer(timer);
|
|
|
|
*/
|
|
|
|
int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
|
|
|
|
{
|
|
|
|
if (timer->expires == expires && timer_pending(timer))
|
|
|
|
return 1;
|
|
|
|
|
|
|
|
return __mod_timer(timer, expires, false, TIMER_PINNED);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(mod_timer_pinned);
|
|
|
|
|
2009-02-18 18:23:29 +07:00
|
|
|
/**
|
|
|
|
* add_timer - start a timer
|
|
|
|
* @timer: the timer to be added
|
|
|
|
*
|
|
|
|
* The kernel will do a ->function(->data) callback from the
|
|
|
|
* timer interrupt at the ->expires point in the future. The
|
|
|
|
* current time is 'jiffies'.
|
|
|
|
*
|
|
|
|
* The timer's ->expires, ->function (and if the handler uses it, ->data)
|
|
|
|
* fields must be set prior calling this function.
|
|
|
|
*
|
|
|
|
* Timers with an ->expires field in the past will be executed in the next
|
|
|
|
* timer tick.
|
|
|
|
*/
|
|
|
|
void add_timer(struct timer_list *timer)
|
|
|
|
{
|
|
|
|
BUG_ON(timer_pending(timer));
|
|
|
|
mod_timer(timer, timer->expires);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(add_timer);
|
|
|
|
|
|
|
|
/**
|
|
|
|
* add_timer_on - start a timer on a particular CPU
|
|
|
|
* @timer: the timer to be added
|
|
|
|
* @cpu: the CPU to start it on
|
|
|
|
*
|
|
|
|
* This is not very scalable on SMP. Double adds are not possible.
|
|
|
|
*/
|
|
|
|
void add_timer_on(struct timer_list *timer, int cpu)
|
|
|
|
{
|
|
|
|
struct tvec_base *base = per_cpu(tvec_bases, cpu);
|
|
|
|
unsigned long flags;
|
|
|
|
|
|
|
|
timer_stats_timer_set_start_info(timer);
|
|
|
|
BUG_ON(timer_pending(timer) || !timer->function);
|
|
|
|
spin_lock_irqsave(&base->lock, flags);
|
|
|
|
timer_set_base(timer, base);
|
2009-08-10 09:48:59 +07:00
|
|
|
debug_activate(timer, timer->expires);
|
2009-02-18 18:23:29 +07:00
|
|
|
internal_add_timer(base, timer);
|
|
|
|
spin_unlock_irqrestore(&base->lock, flags);
|
|
|
|
}
|
2009-05-20 03:49:07 +07:00
|
|
|
EXPORT_SYMBOL_GPL(add_timer_on);
|
2009-02-18 18:23:29 +07:00
|
|
|
|
2006-09-29 15:59:46 +07:00
|
|
|
/**
|
2005-04-17 05:20:36 +07:00
|
|
|
* del_timer - deactive a timer.
|
|
|
|
* @timer: the timer to be deactivated
|
|
|
|
*
|
|
|
|
* del_timer() deactivates a timer - this works on both active and inactive
|
|
|
|
* timers.
|
|
|
|
*
|
|
|
|
* The function returns whether it has deactivated a pending timer or not.
|
|
|
|
* (ie. del_timer() of an inactive timer returns 0, del_timer() of an
|
|
|
|
* active timer returns 1.)
|
|
|
|
*/
|
|
|
|
int del_timer(struct timer_list *timer)
|
|
|
|
{
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base *base;
|
2005-04-17 05:20:36 +07:00
|
|
|
unsigned long flags;
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
int ret = 0;
|
2005-04-17 05:20:36 +07:00
|
|
|
|
2011-11-08 10:48:28 +07:00
|
|
|
debug_assert_init(timer);
|
|
|
|
|
[PATCH] Add debugging feature /proc/timer_stat
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.
Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec
[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 16:28:13 +07:00
|
|
|
timer_stats_timer_clear_start_info(timer);
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
if (timer_pending(timer)) {
|
|
|
|
base = lock_timer_base(timer, &flags);
|
2012-05-26 05:08:57 +07:00
|
|
|
ret = detach_if_pending(timer, base, true);
|
2005-04-17 05:20:36 +07:00
|
|
|
spin_unlock_irqrestore(&base->lock, flags);
|
|
|
|
}
|
|
|
|
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
return ret;
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(del_timer);
|
|
|
|
|
2006-09-29 15:59:46 +07:00
|
|
|
/**
|
|
|
|
* try_to_del_timer_sync - Try to deactivate a timer
|
|
|
|
* @timer: timer do del
|
|
|
|
*
|
2005-06-23 14:08:59 +07:00
|
|
|
* This function tries to deactivate a timer. Upon successful (ret >= 0)
|
|
|
|
* exit the timer is not queued and the handler is not running on any CPU.
|
|
|
|
*/
|
|
|
|
int try_to_del_timer_sync(struct timer_list *timer)
|
|
|
|
{
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base *base;
|
2005-06-23 14:08:59 +07:00
|
|
|
unsigned long flags;
|
|
|
|
int ret = -1;
|
|
|
|
|
2011-11-08 10:48:28 +07:00
|
|
|
debug_assert_init(timer);
|
|
|
|
|
2005-06-23 14:08:59 +07:00
|
|
|
base = lock_timer_base(timer, &flags);
|
|
|
|
|
2012-05-26 05:08:57 +07:00
|
|
|
if (base->running_timer != timer) {
|
|
|
|
timer_stats_timer_clear_start_info(timer);
|
|
|
|
ret = detach_if_pending(timer, base, true);
|
2005-06-23 14:08:59 +07:00
|
|
|
}
|
|
|
|
spin_unlock_irqrestore(&base->lock, flags);
|
|
|
|
|
|
|
|
return ret;
|
|
|
|
}
|
2007-04-27 05:46:56 +07:00
|
|
|
EXPORT_SYMBOL(try_to_del_timer_sync);
|
|
|
|
|
2010-10-21 05:57:31 +07:00
|
|
|
#ifdef CONFIG_SMP
|
2006-09-29 15:59:46 +07:00
|
|
|
/**
|
2005-04-17 05:20:36 +07:00
|
|
|
* del_timer_sync - deactivate a timer and wait for the handler to finish.
|
|
|
|
* @timer: the timer to be deactivated
|
|
|
|
*
|
|
|
|
* This function only differs from del_timer() on SMP: besides deactivating
|
|
|
|
* the timer it also makes sure the handler has finished executing on other
|
|
|
|
* CPUs.
|
|
|
|
*
|
2007-02-10 16:45:59 +07:00
|
|
|
* Synchronization rules: Callers must prevent restarting of the timer,
|
2005-04-17 05:20:36 +07:00
|
|
|
* otherwise this function is meaningless. It must not be called from
|
2012-08-09 01:10:28 +07:00
|
|
|
* interrupt contexts unless the timer is an irqsafe one. The caller must
|
|
|
|
* not hold locks which would prevent completion of the timer's
|
|
|
|
* handler. The timer's handler must not call add_timer_on(). Upon exit the
|
|
|
|
* timer is not queued and the handler is not running on any CPU.
|
2005-04-17 05:20:36 +07:00
|
|
|
*
|
2012-08-09 01:10:28 +07:00
|
|
|
* Note: For !irqsafe timers, you must not hold locks that are held in
|
|
|
|
* interrupt context while calling this function. Even if the lock has
|
|
|
|
* nothing to do with the timer in question. Here's why:
|
2011-02-09 00:39:54 +07:00
|
|
|
*
|
|
|
|
* CPU0 CPU1
|
|
|
|
* ---- ----
|
|
|
|
* <SOFTIRQ>
|
|
|
|
* call_timer_fn();
|
|
|
|
* base->running_timer = mytimer;
|
|
|
|
* spin_lock_irq(somelock);
|
|
|
|
* <IRQ>
|
|
|
|
* spin_lock(somelock);
|
|
|
|
* del_timer_sync(mytimer);
|
|
|
|
* while (base->running_timer == mytimer);
|
|
|
|
*
|
|
|
|
* Now del_timer_sync() will never return and never release somelock.
|
|
|
|
* The interrupt on the other CPU is waiting to grab somelock but
|
|
|
|
* it has interrupted the softirq that CPU0 is waiting to finish.
|
|
|
|
*
|
2005-04-17 05:20:36 +07:00
|
|
|
* The function returns whether it has deactivated a pending timer or not.
|
|
|
|
*/
|
|
|
|
int del_timer_sync(struct timer_list *timer)
|
|
|
|
{
|
2009-01-29 22:03:20 +07:00
|
|
|
#ifdef CONFIG_LOCKDEP
|
2011-02-03 21:09:41 +07:00
|
|
|
unsigned long flags;
|
|
|
|
|
2011-02-09 00:39:54 +07:00
|
|
|
/*
|
|
|
|
* If lockdep gives a backtrace here, please reference
|
|
|
|
* the synchronization rules above.
|
|
|
|
*/
|
2011-02-08 21:18:00 +07:00
|
|
|
local_irq_save(flags);
|
2009-01-29 22:03:20 +07:00
|
|
|
lock_map_acquire(&timer->lockdep_map);
|
|
|
|
lock_map_release(&timer->lockdep_map);
|
2011-02-08 21:18:00 +07:00
|
|
|
local_irq_restore(flags);
|
2009-01-29 22:03:20 +07:00
|
|
|
#endif
|
2010-10-21 05:57:33 +07:00
|
|
|
/*
|
|
|
|
* don't use it in hardirq context, because it
|
|
|
|
* could lead to deadlock.
|
|
|
|
*/
|
2012-08-09 01:10:28 +07:00
|
|
|
WARN_ON(in_irq() && !tbase_get_irqsafe(timer->base));
|
2005-06-23 14:08:59 +07:00
|
|
|
for (;;) {
|
|
|
|
int ret = try_to_del_timer_sync(timer);
|
|
|
|
if (ret >= 0)
|
|
|
|
return ret;
|
2006-07-14 14:24:06 +07:00
|
|
|
cpu_relax();
|
2005-06-23 14:08:59 +07:00
|
|
|
}
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
EXPORT_SYMBOL(del_timer_sync);
|
2005-04-17 05:20:36 +07:00
|
|
|
#endif
|
|
|
|
|
2008-01-30 19:30:00 +07:00
|
|
|
static int cascade(struct tvec_base *base, struct tvec *tv, int index)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
|
|
|
/* cascade all the timers from tv up one level */
|
[PATCH] When CONFIG_BASE_SMALL=1, cascade() may enter an infinite loop
When CONFIG_BASE_SAMLL=1, cascade() in may enter the infinite loop.
Because of CONFIG_BASE_SMALL=1(TVR_BITS=6 and TVN_BITS=4), the list
base->tv5 may cascade into base->tv5. So, the kernel enters the infinite
loop in the function cascade().
I created a test module to verify this bug, and a patch to fix it.
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/timer.h>
#if 0
#include <linux/kdb.h>
#else
#define kdb_printf printk
#endif
#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
#define TVN_SIZE (1 << TVN_BITS)
#define TVR_SIZE (1 << TVR_BITS)
#define TVN_MASK (TVN_SIZE - 1)
#define TVR_MASK (TVR_SIZE - 1)
#define TV_SIZE(N) (N*TVN_BITS + TVR_BITS)
struct timer_list timer0;
struct timer_list dummy_timer1;
struct timer_list dummy_timer2;
void dummy_timer_fun(unsigned long data) {
}
unsigned long j=0;
void check_timer_base(unsigned long data)
{
kdb_printf("check_timer_base %08x\n",jiffies);
mod_timer(&timer0,(jiffies & (~0xFFF)) + 0x1FFF);
}
int init_module(void)
{
init_timer(&timer0);
timer0.data = (unsigned long)0;
timer0.function = check_timer_base;
mod_timer(&timer0,jiffies+1);
init_timer(&dummy_timer1);
dummy_timer1.data = (unsigned long)0;
dummy_timer1.function = dummy_timer_fun;
init_timer(&dummy_timer2);
dummy_timer2.data = (unsigned long)0;
dummy_timer2.function = dummy_timer_fun;
j=jiffies;
j&=(~((1<<TV_SIZE(3))-1));
j+=(1<<TV_SIZE(3));
j+=(1<<TV_SIZE(4));
kdb_printf("mod_timer %08x\n",j);
mod_timer(&dummy_timer1, j );
mod_timer(&dummy_timer2, j );
return 0;
}
void cleanup_module()
{
del_timer_sync(&timer0);
del_timer_sync(&dummy_timer1);
del_timer_sync(&dummy_timer2);
}
(Cleanups from Oleg)
[oleg@tv-sign.ru: use list_replace_init()]
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 16:05:56 +07:00
|
|
|
struct timer_list *timer, *tmp;
|
|
|
|
struct list_head tv_list;
|
|
|
|
|
|
|
|
list_replace_init(tv->vec + index, &tv_list);
|
2005-04-17 05:20:36 +07:00
|
|
|
|
|
|
|
/*
|
[PATCH] When CONFIG_BASE_SMALL=1, cascade() may enter an infinite loop
When CONFIG_BASE_SAMLL=1, cascade() in may enter the infinite loop.
Because of CONFIG_BASE_SMALL=1(TVR_BITS=6 and TVN_BITS=4), the list
base->tv5 may cascade into base->tv5. So, the kernel enters the infinite
loop in the function cascade().
I created a test module to verify this bug, and a patch to fix it.
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/timer.h>
#if 0
#include <linux/kdb.h>
#else
#define kdb_printf printk
#endif
#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
#define TVN_SIZE (1 << TVN_BITS)
#define TVR_SIZE (1 << TVR_BITS)
#define TVN_MASK (TVN_SIZE - 1)
#define TVR_MASK (TVR_SIZE - 1)
#define TV_SIZE(N) (N*TVN_BITS + TVR_BITS)
struct timer_list timer0;
struct timer_list dummy_timer1;
struct timer_list dummy_timer2;
void dummy_timer_fun(unsigned long data) {
}
unsigned long j=0;
void check_timer_base(unsigned long data)
{
kdb_printf("check_timer_base %08x\n",jiffies);
mod_timer(&timer0,(jiffies & (~0xFFF)) + 0x1FFF);
}
int init_module(void)
{
init_timer(&timer0);
timer0.data = (unsigned long)0;
timer0.function = check_timer_base;
mod_timer(&timer0,jiffies+1);
init_timer(&dummy_timer1);
dummy_timer1.data = (unsigned long)0;
dummy_timer1.function = dummy_timer_fun;
init_timer(&dummy_timer2);
dummy_timer2.data = (unsigned long)0;
dummy_timer2.function = dummy_timer_fun;
j=jiffies;
j&=(~((1<<TV_SIZE(3))-1));
j+=(1<<TV_SIZE(3));
j+=(1<<TV_SIZE(4));
kdb_printf("mod_timer %08x\n",j);
mod_timer(&dummy_timer1, j );
mod_timer(&dummy_timer2, j );
return 0;
}
void cleanup_module()
{
del_timer_sync(&timer0);
del_timer_sync(&dummy_timer1);
del_timer_sync(&dummy_timer2);
}
(Cleanups from Oleg)
[oleg@tv-sign.ru: use list_replace_init()]
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 16:05:56 +07:00
|
|
|
* We are removing _all_ timers from the list, so we
|
|
|
|
* don't have to detach them individually.
|
2005-04-17 05:20:36 +07:00
|
|
|
*/
|
[PATCH] When CONFIG_BASE_SMALL=1, cascade() may enter an infinite loop
When CONFIG_BASE_SAMLL=1, cascade() in may enter the infinite loop.
Because of CONFIG_BASE_SMALL=1(TVR_BITS=6 and TVN_BITS=4), the list
base->tv5 may cascade into base->tv5. So, the kernel enters the infinite
loop in the function cascade().
I created a test module to verify this bug, and a patch to fix it.
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/timer.h>
#if 0
#include <linux/kdb.h>
#else
#define kdb_printf printk
#endif
#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
#define TVN_SIZE (1 << TVN_BITS)
#define TVR_SIZE (1 << TVR_BITS)
#define TVN_MASK (TVN_SIZE - 1)
#define TVR_MASK (TVR_SIZE - 1)
#define TV_SIZE(N) (N*TVN_BITS + TVR_BITS)
struct timer_list timer0;
struct timer_list dummy_timer1;
struct timer_list dummy_timer2;
void dummy_timer_fun(unsigned long data) {
}
unsigned long j=0;
void check_timer_base(unsigned long data)
{
kdb_printf("check_timer_base %08x\n",jiffies);
mod_timer(&timer0,(jiffies & (~0xFFF)) + 0x1FFF);
}
int init_module(void)
{
init_timer(&timer0);
timer0.data = (unsigned long)0;
timer0.function = check_timer_base;
mod_timer(&timer0,jiffies+1);
init_timer(&dummy_timer1);
dummy_timer1.data = (unsigned long)0;
dummy_timer1.function = dummy_timer_fun;
init_timer(&dummy_timer2);
dummy_timer2.data = (unsigned long)0;
dummy_timer2.function = dummy_timer_fun;
j=jiffies;
j&=(~((1<<TV_SIZE(3))-1));
j+=(1<<TV_SIZE(3));
j+=(1<<TV_SIZE(4));
kdb_printf("mod_timer %08x\n",j);
mod_timer(&dummy_timer1, j );
mod_timer(&dummy_timer2, j );
return 0;
}
void cleanup_module()
{
del_timer_sync(&timer0);
del_timer_sync(&dummy_timer1);
del_timer_sync(&dummy_timer2);
}
(Cleanups from Oleg)
[oleg@tv-sign.ru: use list_replace_init()]
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 16:05:56 +07:00
|
|
|
list_for_each_entry_safe(timer, tmp, &tv_list, entry) {
|
2007-05-08 14:27:44 +07:00
|
|
|
BUG_ON(tbase_get_base(timer->base) != base);
|
2012-05-26 05:08:57 +07:00
|
|
|
/* No accounting, while moving them */
|
|
|
|
__internal_add_timer(base, timer);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
|
|
|
|
return index;
|
|
|
|
}
|
|
|
|
|
2010-03-13 03:10:29 +07:00
|
|
|
static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
|
|
|
|
unsigned long data)
|
|
|
|
{
|
2013-08-14 19:55:24 +07:00
|
|
|
int count = preempt_count();
|
2010-03-13 03:10:29 +07:00
|
|
|
|
|
|
|
#ifdef CONFIG_LOCKDEP
|
|
|
|
/*
|
|
|
|
* It is permissible to free the timer from inside the
|
|
|
|
* function that is called from it, this we need to take into
|
|
|
|
* account for lockdep too. To avoid bogus "held lock freed"
|
|
|
|
* warnings as well as problems when looking into
|
|
|
|
* timer->lockdep_map, make a copy and use that here.
|
|
|
|
*/
|
lockdep: fix oops in processing workqueue
Under memory load, on x86_64, with lockdep enabled, the workqueue's
process_one_work() has been seen to oops in __lock_acquire(), barfing
on a 0xffffffff00000000 pointer in the lockdep_map's class_cache[].
Because it's permissible to free a work_struct from its callout function,
the map used is an onstack copy of the map given in the work_struct: and
that copy is made without any locking.
Surprisingly, gcc (4.5.1 in Hugh's case) uses "rep movsl" rather than
"rep movsq" for that structure copy: which might race with a workqueue
user's wait_on_work() doing lock_map_acquire() on the source of the
copy, putting a pointer into the class_cache[], but only in time for
the top half of that pointer to be copied to the destination map.
Boom when process_one_work() subsequently does lock_map_acquire()
on its onstack copy of the lockdep_map.
Fix this, and a similar instance in call_timer_fn(), with a
lockdep_copy_map() function which additionally NULLs the class_cache[].
Note: this oops was actually seen on 3.4-next, where flush_work() newly
does the racing lock_map_acquire(); but Tejun points out that 3.4 and
earlier are already vulnerable to the same through wait_on_work().
* Patch orginally from Peter. Hugh modified it a bit and wrote the
description.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Reported-by: Hugh Dickins <hughd@google.com>
LKML-Reference: <alpine.LSU.2.00.1205070951170.1544@eggly.anvils>
Signed-off-by: Tejun Heo <tj@kernel.org>
2012-05-15 22:06:19 +07:00
|
|
|
struct lockdep_map lockdep_map;
|
|
|
|
|
|
|
|
lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
|
2010-03-13 03:10:29 +07:00
|
|
|
#endif
|
|
|
|
/*
|
|
|
|
* Couple the lock chain with the lock chain at
|
|
|
|
* del_timer_sync() by acquiring the lock_map around the fn()
|
|
|
|
* call here and in del_timer_sync().
|
|
|
|
*/
|
|
|
|
lock_map_acquire(&lockdep_map);
|
|
|
|
|
|
|
|
trace_timer_expire_entry(timer);
|
|
|
|
fn(data);
|
|
|
|
trace_timer_expire_exit(timer);
|
|
|
|
|
|
|
|
lock_map_release(&lockdep_map);
|
|
|
|
|
2013-08-14 19:55:24 +07:00
|
|
|
if (count != preempt_count()) {
|
2010-03-13 02:13:23 +07:00
|
|
|
WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
|
2013-08-14 19:55:24 +07:00
|
|
|
fn, count, preempt_count());
|
2010-03-13 02:13:23 +07:00
|
|
|
/*
|
|
|
|
* Restore the preempt count. That gives us a decent
|
|
|
|
* chance to survive and extract information. If the
|
|
|
|
* callback kept a lock held, bad luck, but not worse
|
|
|
|
* than the BUG() we had.
|
|
|
|
*/
|
2013-08-14 19:55:24 +07:00
|
|
|
preempt_count_set(count);
|
2010-03-13 03:10:29 +07:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2006-09-29 15:59:46 +07:00
|
|
|
#define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
|
|
|
|
|
|
|
|
/**
|
2005-04-17 05:20:36 +07:00
|
|
|
* __run_timers - run all expired timers (if any) on this CPU.
|
|
|
|
* @base: the timer vector to be processed.
|
|
|
|
*
|
|
|
|
* This function cascades all vectors and executes all expired timer
|
|
|
|
* vectors.
|
|
|
|
*/
|
2008-01-30 19:30:00 +07:00
|
|
|
static inline void __run_timers(struct tvec_base *base)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
|
|
|
struct timer_list *timer;
|
|
|
|
|
2006-03-31 17:30:30 +07:00
|
|
|
spin_lock_irq(&base->lock);
|
2013-12-16 20:57:10 +07:00
|
|
|
if (catchup_timer_jiffies(base)) {
|
|
|
|
spin_unlock_irq(&base->lock);
|
|
|
|
return;
|
|
|
|
}
|
2005-04-17 05:20:36 +07:00
|
|
|
while (time_after_eq(jiffies, base->timer_jiffies)) {
|
2006-06-23 16:05:55 +07:00
|
|
|
struct list_head work_list;
|
2005-04-17 05:20:36 +07:00
|
|
|
struct list_head *head = &work_list;
|
2007-07-19 15:49:16 +07:00
|
|
|
int index = base->timer_jiffies & TVR_MASK;
|
2006-06-23 16:05:55 +07:00
|
|
|
|
2005-04-17 05:20:36 +07:00
|
|
|
/*
|
|
|
|
* Cascade timers:
|
|
|
|
*/
|
|
|
|
if (!index &&
|
|
|
|
(!cascade(base, &base->tv2, INDEX(0))) &&
|
|
|
|
(!cascade(base, &base->tv3, INDEX(1))) &&
|
|
|
|
!cascade(base, &base->tv4, INDEX(2)))
|
|
|
|
cascade(base, &base->tv5, INDEX(3));
|
2006-06-23 16:05:55 +07:00
|
|
|
++base->timer_jiffies;
|
2014-03-18 14:53:15 +07:00
|
|
|
list_replace_init(base->tv1.vec + index, head);
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
while (!list_empty(head)) {
|
2005-04-17 05:20:36 +07:00
|
|
|
void (*fn)(unsigned long);
|
|
|
|
unsigned long data;
|
2012-08-09 01:10:28 +07:00
|
|
|
bool irqsafe;
|
2005-04-17 05:20:36 +07:00
|
|
|
|
Introduce a handy list_first_entry macro
There are many places in the kernel where the construction like
foo = list_entry(head->next, struct foo_struct, list);
are used.
The code might look more descriptive and neat if using the macro
list_first_entry(head, type, member) \
list_entry((head)->next, type, member)
Here is the macro itself and the examples of its usage in the generic code.
If it will turn out to be useful, I can prepare the set of patches to
inject in into arch-specific code, drivers, networking, etc.
Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-08 14:30:19 +07:00
|
|
|
timer = list_first_entry(head, struct timer_list,entry);
|
2007-07-19 15:49:16 +07:00
|
|
|
fn = timer->function;
|
|
|
|
data = timer->data;
|
2012-08-09 01:10:28 +07:00
|
|
|
irqsafe = tbase_get_irqsafe(timer->base);
|
2005-04-17 05:20:36 +07:00
|
|
|
|
[PATCH] Add debugging feature /proc/timer_stat
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.
Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec
[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 16:28:13 +07:00
|
|
|
timer_stats_account_timer(timer);
|
|
|
|
|
2010-10-21 05:57:31 +07:00
|
|
|
base->running_timer = timer;
|
2012-05-26 05:08:58 +07:00
|
|
|
detach_expired_timer(timer, base);
|
2009-01-29 22:03:20 +07:00
|
|
|
|
2012-08-09 01:10:28 +07:00
|
|
|
if (irqsafe) {
|
|
|
|
spin_unlock(&base->lock);
|
|
|
|
call_timer_fn(timer, fn, data);
|
|
|
|
spin_lock(&base->lock);
|
|
|
|
} else {
|
|
|
|
spin_unlock_irq(&base->lock);
|
|
|
|
call_timer_fn(timer, fn, data);
|
|
|
|
spin_lock_irq(&base->lock);
|
|
|
|
}
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
}
|
2010-10-21 05:57:31 +07:00
|
|
|
base->running_timer = NULL;
|
2006-03-31 17:30:30 +07:00
|
|
|
spin_unlock_irq(&base->lock);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
|
2011-08-11 04:21:01 +07:00
|
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
2005-04-17 05:20:36 +07:00
|
|
|
/*
|
|
|
|
* Find out when the next timer event is due to happen. This
|
2009-08-26 04:35:41 +07:00
|
|
|
* is used on S/390 to stop all activity when a CPU is idle.
|
|
|
|
* This function needs to be called with interrupts disabled.
|
2005-04-17 05:20:36 +07:00
|
|
|
*/
|
2008-01-30 19:30:00 +07:00
|
|
|
static unsigned long __next_timer_interrupt(struct tvec_base *base)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
2007-02-16 16:27:46 +07:00
|
|
|
unsigned long timer_jiffies = base->timer_jiffies;
|
2007-05-30 04:47:39 +07:00
|
|
|
unsigned long expires = timer_jiffies + NEXT_TIMER_MAX_DELTA;
|
2007-02-16 16:27:46 +07:00
|
|
|
int index, slot, array, found = 0;
|
2005-04-17 05:20:36 +07:00
|
|
|
struct timer_list *nte;
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec *varray[4];
|
2005-04-17 05:20:36 +07:00
|
|
|
|
|
|
|
/* Look for timer events in tv1. */
|
2007-02-16 16:27:46 +07:00
|
|
|
index = slot = timer_jiffies & TVR_MASK;
|
2005-04-17 05:20:36 +07:00
|
|
|
do {
|
2007-02-16 16:27:46 +07:00
|
|
|
list_for_each_entry(nte, base->tv1.vec + slot, entry) {
|
2007-07-19 15:49:16 +07:00
|
|
|
if (tbase_get_deferrable(nte->base))
|
|
|
|
continue;
|
2007-05-08 14:27:44 +07:00
|
|
|
|
2007-02-16 16:27:46 +07:00
|
|
|
found = 1;
|
2005-04-17 05:20:36 +07:00
|
|
|
expires = nte->expires;
|
2007-02-16 16:27:46 +07:00
|
|
|
/* Look at the cascade bucket(s)? */
|
|
|
|
if (!index || slot < index)
|
|
|
|
goto cascade;
|
|
|
|
return expires;
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
2007-02-16 16:27:46 +07:00
|
|
|
slot = (slot + 1) & TVR_MASK;
|
|
|
|
} while (slot != index);
|
|
|
|
|
|
|
|
cascade:
|
|
|
|
/* Calculate the next cascade event */
|
|
|
|
if (index)
|
|
|
|
timer_jiffies += TVR_SIZE - index;
|
|
|
|
timer_jiffies >>= TVR_BITS;
|
2005-04-17 05:20:36 +07:00
|
|
|
|
|
|
|
/* Check tv2-tv5. */
|
|
|
|
varray[0] = &base->tv2;
|
|
|
|
varray[1] = &base->tv3;
|
|
|
|
varray[2] = &base->tv4;
|
|
|
|
varray[3] = &base->tv5;
|
2007-02-16 16:27:46 +07:00
|
|
|
|
|
|
|
for (array = 0; array < 4; array++) {
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec *varp = varray[array];
|
2007-02-16 16:27:46 +07:00
|
|
|
|
|
|
|
index = slot = timer_jiffies & TVN_MASK;
|
2005-04-17 05:20:36 +07:00
|
|
|
do {
|
2007-02-16 16:27:46 +07:00
|
|
|
list_for_each_entry(nte, varp->vec + slot, entry) {
|
2009-05-02 03:10:23 +07:00
|
|
|
if (tbase_get_deferrable(nte->base))
|
|
|
|
continue;
|
|
|
|
|
2007-02-16 16:27:46 +07:00
|
|
|
found = 1;
|
2005-04-17 05:20:36 +07:00
|
|
|
if (time_before(nte->expires, expires))
|
|
|
|
expires = nte->expires;
|
2007-02-16 16:27:46 +07:00
|
|
|
}
|
|
|
|
/*
|
|
|
|
* Do we still search for the first timer or are
|
|
|
|
* we looking up the cascade buckets ?
|
|
|
|
*/
|
|
|
|
if (found) {
|
|
|
|
/* Look at the cascade bucket(s)? */
|
|
|
|
if (!index || slot < index)
|
|
|
|
break;
|
|
|
|
return expires;
|
|
|
|
}
|
|
|
|
slot = (slot + 1) & TVN_MASK;
|
|
|
|
} while (slot != index);
|
|
|
|
|
|
|
|
if (index)
|
|
|
|
timer_jiffies += TVN_SIZE - index;
|
|
|
|
timer_jiffies >>= TVN_BITS;
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
2007-02-16 16:27:46 +07:00
|
|
|
return expires;
|
|
|
|
}
|
2006-03-07 06:42:45 +07:00
|
|
|
|
2007-02-16 16:27:46 +07:00
|
|
|
/*
|
|
|
|
* Check, if the next hrtimer event is before the next timer wheel
|
|
|
|
* event:
|
|
|
|
*/
|
|
|
|
static unsigned long cmp_next_hrtimer_event(unsigned long now,
|
|
|
|
unsigned long expires)
|
|
|
|
{
|
|
|
|
ktime_t hr_delta = hrtimer_get_next_event();
|
|
|
|
struct timespec tsdelta;
|
2007-03-25 19:31:17 +07:00
|
|
|
unsigned long delta;
|
2007-02-16 16:27:46 +07:00
|
|
|
|
|
|
|
if (hr_delta.tv64 == KTIME_MAX)
|
|
|
|
return expires;
|
2006-05-21 05:00:24 +07:00
|
|
|
|
2007-03-25 19:31:17 +07:00
|
|
|
/*
|
|
|
|
* Expired timer available, let it expire in the next tick
|
|
|
|
*/
|
|
|
|
if (hr_delta.tv64 <= 0)
|
|
|
|
return now + 1;
|
2006-03-07 06:42:45 +07:00
|
|
|
|
2007-02-16 16:27:46 +07:00
|
|
|
tsdelta = ktime_to_timespec(hr_delta);
|
2007-03-25 19:31:17 +07:00
|
|
|
delta = timespec_to_jiffies(&tsdelta);
|
2007-05-30 04:47:39 +07:00
|
|
|
|
|
|
|
/*
|
|
|
|
* Limit the delta to the max value, which is checked in
|
|
|
|
* tick_nohz_stop_sched_tick():
|
|
|
|
*/
|
|
|
|
if (delta > NEXT_TIMER_MAX_DELTA)
|
|
|
|
delta = NEXT_TIMER_MAX_DELTA;
|
|
|
|
|
2007-03-25 19:31:17 +07:00
|
|
|
/*
|
|
|
|
* Take rounding errors in to account and make sure, that it
|
|
|
|
* expires in the next tick. Otherwise we go into an endless
|
|
|
|
* ping pong due to tick_nohz_stop_sched_tick() retriggering
|
|
|
|
* the timer softirq
|
|
|
|
*/
|
|
|
|
if (delta < 1)
|
|
|
|
delta = 1;
|
|
|
|
now += delta;
|
2007-02-16 16:27:46 +07:00
|
|
|
if (time_before(now, expires))
|
|
|
|
return now;
|
2005-04-17 05:20:36 +07:00
|
|
|
return expires;
|
|
|
|
}
|
2007-02-16 16:27:46 +07:00
|
|
|
|
|
|
|
/**
|
2007-11-06 05:51:10 +07:00
|
|
|
* get_next_timer_interrupt - return the jiffy of the next pending timer
|
2007-03-01 11:12:13 +07:00
|
|
|
* @now: current time (in jiffies)
|
2007-02-16 16:27:46 +07:00
|
|
|
*/
|
2007-02-16 16:27:47 +07:00
|
|
|
unsigned long get_next_timer_interrupt(unsigned long now)
|
2007-02-16 16:27:46 +07:00
|
|
|
{
|
2010-12-01 03:05:53 +07:00
|
|
|
struct tvec_base *base = __this_cpu_read(tvec_bases);
|
2012-05-26 05:08:59 +07:00
|
|
|
unsigned long expires = now + NEXT_TIMER_MAX_DELTA;
|
2007-02-16 16:27:46 +07:00
|
|
|
|
2010-12-01 16:11:09 +07:00
|
|
|
/*
|
|
|
|
* Pretend that there is no timer pending if the cpu is offline.
|
|
|
|
* Possible pending timers will be migrated later to an active cpu.
|
|
|
|
*/
|
|
|
|
if (cpu_is_offline(smp_processor_id()))
|
2012-05-26 05:08:59 +07:00
|
|
|
return expires;
|
|
|
|
|
2007-02-16 16:27:46 +07:00
|
|
|
spin_lock(&base->lock);
|
2012-05-26 05:08:59 +07:00
|
|
|
if (base->active_timers) {
|
|
|
|
if (time_before_eq(base->next_timer, base->timer_jiffies))
|
|
|
|
base->next_timer = __next_timer_interrupt(base);
|
|
|
|
expires = base->next_timer;
|
|
|
|
}
|
2007-02-16 16:27:46 +07:00
|
|
|
spin_unlock(&base->lock);
|
|
|
|
|
|
|
|
if (time_before_eq(expires, now))
|
|
|
|
return now;
|
|
|
|
|
|
|
|
return cmp_next_hrtimer_event(now, expires);
|
|
|
|
}
|
2005-04-17 05:20:36 +07:00
|
|
|
#endif
|
|
|
|
|
|
|
|
/*
|
2007-10-18 17:06:11 +07:00
|
|
|
* Called from the timer interrupt handler to charge one tick to the current
|
2005-04-17 05:20:36 +07:00
|
|
|
* process. user_tick is 1 if the tick is user time, 0 for system.
|
|
|
|
*/
|
|
|
|
void update_process_times(int user_tick)
|
|
|
|
{
|
|
|
|
struct task_struct *p = current;
|
|
|
|
int cpu = smp_processor_id();
|
|
|
|
|
|
|
|
/* Note: this timer irq context must be accounted for as well. */
|
2007-11-10 04:39:38 +07:00
|
|
|
account_process_tick(p, user_tick);
|
2005-04-17 05:20:36 +07:00
|
|
|
run_local_timers();
|
2009-08-23 03:56:51 +07:00
|
|
|
rcu_check_callbacks(cpu, user_tick);
|
2010-10-14 13:01:34 +07:00
|
|
|
#ifdef CONFIG_IRQ_WORK
|
|
|
|
if (in_irq())
|
|
|
|
irq_work_run();
|
|
|
|
#endif
|
2005-04-17 05:20:36 +07:00
|
|
|
scheduler_tick();
|
2007-07-19 15:49:16 +07:00
|
|
|
run_posix_cpu_timers(p);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* This function runs timers and the timer-tq in bottom half context.
|
|
|
|
*/
|
|
|
|
static void run_timer_softirq(struct softirq_action *h)
|
|
|
|
{
|
2010-12-01 03:05:53 +07:00
|
|
|
struct tvec_base *base = __this_cpu_read(tvec_bases);
|
2005-04-17 05:20:36 +07:00
|
|
|
|
2008-01-26 03:08:31 +07:00
|
|
|
hrtimer_run_pending();
|
[PATCH] Add debugging feature /proc/timer_stat
Add /proc/timer_stats support: debugging feature to profile timer expiration.
Both the starting site, process/PID and the expiration function is captured.
This allows the quick identification of timer event sources in a system.
Sample output:
# echo 1 > /proc/timer_stats
# cat /proc/timer_stats
Timer Stats Version: v0.1
Sample period: 4.010 s
24, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
11, 0 swapper sk_reset_timer (tcp_delack_timer)
6, 0 swapper hrtimer_stop_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
17, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
2, 1 swapper queue_delayed_work_on (delayed_work_timer_fn)
4, 2050 pcscd do_nanosleep (hrtimer_wakeup)
5, 4179 sshd sk_reset_timer (tcp_write_timer)
4, 2248 yum-updatesd schedule_timeout (process_timeout)
18, 0 swapper hrtimer_restart_sched_tick (hrtimer_sched_tick)
3, 0 swapper sk_reset_timer (tcp_delack_timer)
1, 1 swapper neigh_table_init_no_netlink (neigh_periodic_timer)
2, 1 swapper e1000_up (e1000_watchdog)
1, 1 init schedule_timeout (process_timeout)
100 total events, 25.24 events/sec
[ cleanups and hrtimers support from Thomas Gleixner <tglx@linutronix.de> ]
[bunk@stusta.de: nr_entries can become static]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-16 16:28:13 +07:00
|
|
|
|
2005-04-17 05:20:36 +07:00
|
|
|
if (time_after_eq(jiffies, base->timer_jiffies))
|
|
|
|
__run_timers(base);
|
|
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
|
|
* Called by the local, per-CPU timer interrupt on SMP.
|
|
|
|
*/
|
|
|
|
void run_local_timers(void)
|
|
|
|
{
|
2008-01-26 03:08:31 +07:00
|
|
|
hrtimer_run_queues();
|
2005-04-17 05:20:36 +07:00
|
|
|
raise_softirq(TIMER_SOFTIRQ);
|
|
|
|
}
|
|
|
|
|
|
|
|
#ifdef __ARCH_WANT_SYS_ALARM
|
|
|
|
|
|
|
|
/*
|
|
|
|
* For backwards compatibility? This can be done in libc so Alpha
|
|
|
|
* and all newer ports shouldn't need it.
|
|
|
|
*/
|
2009-01-14 20:14:03 +07:00
|
|
|
SYSCALL_DEFINE1(alarm, unsigned int, seconds)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
2006-03-25 18:06:33 +07:00
|
|
|
return alarm_setitimer(seconds);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
|
|
|
|
#endif
|
|
|
|
|
|
|
|
static void process_timeout(unsigned long __data)
|
|
|
|
{
|
2006-07-03 14:25:41 +07:00
|
|
|
wake_up_process((struct task_struct *)__data);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* schedule_timeout - sleep until timeout
|
|
|
|
* @timeout: timeout value in jiffies
|
|
|
|
*
|
|
|
|
* Make the current task sleep until @timeout jiffies have
|
|
|
|
* elapsed. The routine will return immediately unless
|
|
|
|
* the current task state has been set (see set_current_state()).
|
|
|
|
*
|
|
|
|
* You can set the task state as follows -
|
|
|
|
*
|
|
|
|
* %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
|
|
|
|
* pass before the routine returns. The routine will return 0
|
|
|
|
*
|
|
|
|
* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
|
|
|
|
* delivered to the current task. In this case the remaining time
|
|
|
|
* in jiffies will be returned, or 0 if the timer expired in time
|
|
|
|
*
|
|
|
|
* The current task state is guaranteed to be TASK_RUNNING when this
|
|
|
|
* routine returns.
|
|
|
|
*
|
|
|
|
* Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
|
|
|
|
* the CPU away without a bound on the timeout. In this case the return
|
|
|
|
* value will be %MAX_SCHEDULE_TIMEOUT.
|
|
|
|
*
|
|
|
|
* In all cases the return value is guaranteed to be non-negative.
|
|
|
|
*/
|
2008-02-08 19:19:53 +07:00
|
|
|
signed long __sched schedule_timeout(signed long timeout)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
|
|
|
struct timer_list timer;
|
|
|
|
unsigned long expire;
|
|
|
|
|
|
|
|
switch (timeout)
|
|
|
|
{
|
|
|
|
case MAX_SCHEDULE_TIMEOUT:
|
|
|
|
/*
|
|
|
|
* These two special cases are useful to be comfortable
|
|
|
|
* in the caller. Nothing more. We could take
|
|
|
|
* MAX_SCHEDULE_TIMEOUT from one of the negative value
|
|
|
|
* but I' d like to return a valid offset (>=0) to allow
|
|
|
|
* the caller to do everything it want with the retval.
|
|
|
|
*/
|
|
|
|
schedule();
|
|
|
|
goto out;
|
|
|
|
default:
|
|
|
|
/*
|
|
|
|
* Another bit of PARANOID. Note that the retval will be
|
|
|
|
* 0 since no piece of kernel is supposed to do a check
|
|
|
|
* for a negative retval of schedule_timeout() (since it
|
|
|
|
* should never happens anyway). You just have the printk()
|
|
|
|
* that will tell you if something is gone wrong and where.
|
|
|
|
*/
|
2006-12-22 16:10:14 +07:00
|
|
|
if (timeout < 0) {
|
2005-04-17 05:20:36 +07:00
|
|
|
printk(KERN_ERR "schedule_timeout: wrong timeout "
|
2006-12-22 16:10:14 +07:00
|
|
|
"value %lx\n", timeout);
|
|
|
|
dump_stack();
|
2005-04-17 05:20:36 +07:00
|
|
|
current->state = TASK_RUNNING;
|
|
|
|
goto out;
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
expire = timeout + jiffies;
|
|
|
|
|
2008-04-30 14:55:03 +07:00
|
|
|
setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
|
2009-04-16 13:43:26 +07:00
|
|
|
__mod_timer(&timer, expire, false, TIMER_NOT_PINNED);
|
2005-04-17 05:20:36 +07:00
|
|
|
schedule();
|
|
|
|
del_singleshot_timer_sync(&timer);
|
|
|
|
|
2008-04-30 14:55:03 +07:00
|
|
|
/* Remove the timer from the object tracker */
|
|
|
|
destroy_timer_on_stack(&timer);
|
|
|
|
|
2005-04-17 05:20:36 +07:00
|
|
|
timeout = expire - jiffies;
|
|
|
|
|
|
|
|
out:
|
|
|
|
return timeout < 0 ? 0 : timeout;
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(schedule_timeout);
|
|
|
|
|
2005-09-13 15:25:15 +07:00
|
|
|
/*
|
|
|
|
* We can use __set_current_state() here because schedule_timeout() calls
|
|
|
|
* schedule() unconditionally.
|
|
|
|
*/
|
2005-09-10 14:27:21 +07:00
|
|
|
signed long __sched schedule_timeout_interruptible(signed long timeout)
|
|
|
|
{
|
2005-10-31 06:01:42 +07:00
|
|
|
__set_current_state(TASK_INTERRUPTIBLE);
|
|
|
|
return schedule_timeout(timeout);
|
2005-09-10 14:27:21 +07:00
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(schedule_timeout_interruptible);
|
|
|
|
|
2007-12-06 23:59:46 +07:00
|
|
|
signed long __sched schedule_timeout_killable(signed long timeout)
|
|
|
|
{
|
|
|
|
__set_current_state(TASK_KILLABLE);
|
|
|
|
return schedule_timeout(timeout);
|
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(schedule_timeout_killable);
|
|
|
|
|
2005-09-10 14:27:21 +07:00
|
|
|
signed long __sched schedule_timeout_uninterruptible(signed long timeout)
|
|
|
|
{
|
2005-10-31 06:01:42 +07:00
|
|
|
__set_current_state(TASK_UNINTERRUPTIBLE);
|
|
|
|
return schedule_timeout(timeout);
|
2005-09-10 14:27:21 +07:00
|
|
|
}
|
|
|
|
EXPORT_SYMBOL(schedule_timeout_uninterruptible);
|
|
|
|
|
2013-06-20 01:53:51 +07:00
|
|
|
static int init_timers_cpu(int cpu)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
|
|
|
int j;
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base *base;
|
2013-06-20 01:53:51 +07:00
|
|
|
static char tvec_base_done[NR_CPUS];
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
|
2006-04-11 12:53:58 +07:00
|
|
|
if (!tvec_base_done[cpu]) {
|
2006-03-24 18:15:54 +07:00
|
|
|
static char boot_done;
|
|
|
|
|
|
|
|
if (boot_done) {
|
2006-04-11 12:53:58 +07:00
|
|
|
/*
|
|
|
|
* The APs use this path later in boot
|
|
|
|
*/
|
2013-11-16 05:15:31 +07:00
|
|
|
base = kzalloc_node(sizeof(*base), GFP_KERNEL,
|
|
|
|
cpu_to_node(cpu));
|
2006-03-24 18:15:54 +07:00
|
|
|
if (!base)
|
|
|
|
return -ENOMEM;
|
2007-05-08 14:27:44 +07:00
|
|
|
|
2014-02-28 15:45:22 +07:00
|
|
|
/* Make sure tvec_base has TIMER_FLAG_MASK bits free */
|
|
|
|
if (WARN_ON(base != tbase_get_base(base))) {
|
2007-05-08 14:27:44 +07:00
|
|
|
kfree(base);
|
|
|
|
return -ENOMEM;
|
|
|
|
}
|
2006-04-11 12:53:58 +07:00
|
|
|
per_cpu(tvec_bases, cpu) = base;
|
2006-03-24 18:15:54 +07:00
|
|
|
} else {
|
2006-04-11 12:53:58 +07:00
|
|
|
/*
|
|
|
|
* This is for the boot CPU - we use compile-time
|
|
|
|
* static initialisation because per-cpu memory isn't
|
|
|
|
* ready yet and because the memory allocators are not
|
|
|
|
* initialised either.
|
|
|
|
*/
|
2006-03-24 18:15:54 +07:00
|
|
|
boot_done = 1;
|
2006-04-11 12:53:58 +07:00
|
|
|
base = &boot_tvec_bases;
|
2006-03-24 18:15:54 +07:00
|
|
|
}
|
timer: Don't reinitialize the cpu base lock during CPU_UP_PREPARE
An inactive timer's base can refer to a offline cpu's base.
In the current code, cpu_base's lock is blindly reinitialized each
time a CPU is brought up. If a CPU is brought online during the period
that another thread is trying to modify an inactive timer on that CPU
with holding its timer base lock, then the lock will be reinitialized
under its feet. This leads to following SPIN_BUG().
<0> BUG: spinlock already unlocked on CPU#3, kworker/u:3/1466
<0> lock: 0xe3ebe000, .magic: dead4ead, .owner: kworker/u:3/1466, .owner_cpu: 1
<4> [<c0013dc4>] (unwind_backtrace+0x0/0x11c) from [<c026e794>] (do_raw_spin_unlock+0x40/0xcc)
<4> [<c026e794>] (do_raw_spin_unlock+0x40/0xcc) from [<c076c160>] (_raw_spin_unlock+0x8/0x30)
<4> [<c076c160>] (_raw_spin_unlock+0x8/0x30) from [<c009b858>] (mod_timer+0x294/0x310)
<4> [<c009b858>] (mod_timer+0x294/0x310) from [<c00a5e04>] (queue_delayed_work_on+0x104/0x120)
<4> [<c00a5e04>] (queue_delayed_work_on+0x104/0x120) from [<c04eae00>] (sdhci_msm_bus_voting+0x88/0x9c)
<4> [<c04eae00>] (sdhci_msm_bus_voting+0x88/0x9c) from [<c04d8780>] (sdhci_disable+0x40/0x48)
<4> [<c04d8780>] (sdhci_disable+0x40/0x48) from [<c04bf300>] (mmc_release_host+0x4c/0xb0)
<4> [<c04bf300>] (mmc_release_host+0x4c/0xb0) from [<c04c7aac>] (mmc_sd_detect+0x90/0xfc)
<4> [<c04c7aac>] (mmc_sd_detect+0x90/0xfc) from [<c04c2504>] (mmc_rescan+0x7c/0x2c4)
<4> [<c04c2504>] (mmc_rescan+0x7c/0x2c4) from [<c00a6a7c>] (process_one_work+0x27c/0x484)
<4> [<c00a6a7c>] (process_one_work+0x27c/0x484) from [<c00a6e94>] (worker_thread+0x210/0x3b0)
<4> [<c00a6e94>] (worker_thread+0x210/0x3b0) from [<c00aad9c>] (kthread+0x80/0x8c)
<4> [<c00aad9c>] (kthread+0x80/0x8c) from [<c000ea80>] (kernel_thread_exit+0x0/0x8)
As an example, this particular crash occurred when CPU #3 is executing
mod_timer() on an inactive timer whose base is refered to offlined CPU
#2. The code locked the timer_base corresponding to CPU #2. Before it
could proceed, CPU #2 came online and reinitialized the spinlock
corresponding to its base. Thus now CPU #3 held a lock which was
reinitialized. When CPU #3 finally ended up unlocking the old cpu_base
corresponding to CPU #2, we hit the above SPIN_BUG().
CPU #0 CPU #3 CPU #2
------ ------- -------
..... ...... <Offline>
mod_timer()
lock_timer_base
spin_lock_irqsave(&base->lock)
cpu_up(2) ..... ......
init_timers_cpu()
.... ..... spin_lock_init(&base->lock)
..... spin_unlock_irqrestore(&base->lock) ......
<spin_bug>
Allocation of per_cpu timer vector bases is done only once under
"tvec_base_done[]" check. In the current code, spinlock_initialization
of base->lock isn't under this check. When a CPU is up each time the
base lock is reinitialized. Move base spinlock initialization under
the check.
Signed-off-by: Tirupathi Reddy <tirupath@codeaurora.org>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/1368520142-4136-1-git-send-email-tirupath@codeaurora.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2013-05-14 15:29:02 +07:00
|
|
|
spin_lock_init(&base->lock);
|
2006-04-11 12:53:58 +07:00
|
|
|
tvec_base_done[cpu] = 1;
|
2014-06-22 06:29:13 +07:00
|
|
|
base->cpu = cpu;
|
2006-04-11 12:53:58 +07:00
|
|
|
} else {
|
|
|
|
base = per_cpu(tvec_bases, cpu);
|
2006-03-24 18:15:54 +07:00
|
|
|
}
|
2006-04-11 12:53:58 +07:00
|
|
|
|
2006-07-03 14:25:10 +07:00
|
|
|
|
2005-04-17 05:20:36 +07:00
|
|
|
for (j = 0; j < TVN_SIZE; j++) {
|
|
|
|
INIT_LIST_HEAD(base->tv5.vec + j);
|
|
|
|
INIT_LIST_HEAD(base->tv4.vec + j);
|
|
|
|
INIT_LIST_HEAD(base->tv3.vec + j);
|
|
|
|
INIT_LIST_HEAD(base->tv2.vec + j);
|
|
|
|
}
|
|
|
|
for (j = 0; j < TVR_SIZE; j++)
|
|
|
|
INIT_LIST_HEAD(base->tv1.vec + j);
|
|
|
|
|
|
|
|
base->timer_jiffies = jiffies;
|
2009-07-22 01:25:05 +07:00
|
|
|
base->next_timer = base->timer_jiffies;
|
2012-05-26 05:08:58 +07:00
|
|
|
base->active_timers = 0;
|
2014-01-15 11:20:43 +07:00
|
|
|
base->all_timers = 0;
|
2006-03-24 18:15:54 +07:00
|
|
|
return 0;
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
2008-01-30 19:30:00 +07:00
|
|
|
static void migrate_timer_list(struct tvec_base *new_base, struct list_head *head)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
|
|
|
struct timer_list *timer;
|
|
|
|
|
|
|
|
while (!list_empty(head)) {
|
Introduce a handy list_first_entry macro
There are many places in the kernel where the construction like
foo = list_entry(head->next, struct foo_struct, list);
are used.
The code might look more descriptive and neat if using the macro
list_first_entry(head, type, member) \
list_entry((head)->next, type, member)
Here is the macro itself and the examples of its usage in the generic code.
If it will turn out to be useful, I can prepare the set of patches to
inject in into arch-specific code, drivers, networking, etc.
Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Cc: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-08 14:30:19 +07:00
|
|
|
timer = list_first_entry(head, struct timer_list, entry);
|
2012-05-26 05:08:58 +07:00
|
|
|
/* We ignore the accounting on the dying cpu */
|
2012-05-26 05:08:57 +07:00
|
|
|
detach_timer(timer, false);
|
2007-05-08 14:27:44 +07:00
|
|
|
timer_set_base(timer, new_base);
|
2005-04-17 05:20:36 +07:00
|
|
|
internal_add_timer(new_base, timer);
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2013-06-20 01:53:51 +07:00
|
|
|
static void migrate_timers(int cpu)
|
2005-04-17 05:20:36 +07:00
|
|
|
{
|
2008-01-30 19:30:00 +07:00
|
|
|
struct tvec_base *old_base;
|
|
|
|
struct tvec_base *new_base;
|
2005-04-17 05:20:36 +07:00
|
|
|
int i;
|
|
|
|
|
|
|
|
BUG_ON(cpu_online(cpu));
|
2006-03-24 18:15:54 +07:00
|
|
|
old_base = per_cpu(tvec_bases, cpu);
|
|
|
|
new_base = get_cpu_var(tvec_bases);
|
2008-08-21 06:46:04 +07:00
|
|
|
/*
|
|
|
|
* The caller is globally serialized and nobody else
|
|
|
|
* takes two locks at once, deadlock is not possible.
|
|
|
|
*/
|
|
|
|
spin_lock_irq(&new_base->lock);
|
2008-04-05 01:54:10 +07:00
|
|
|
spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
|
2006-03-31 17:30:30 +07:00
|
|
|
|
|
|
|
BUG_ON(old_base->running_timer);
|
2005-04-17 05:20:36 +07:00
|
|
|
|
|
|
|
for (i = 0; i < TVR_SIZE; i++)
|
[PATCH] timers fixes/improvements
This patch tries to solve following problems:
1. del_timer_sync() is racy. The timer can be fired again after
del_timer_sync have checked all cpus and before it will recheck
timer_pending().
2. It has scalability problems. All cpus are scanned to determine
if the timer is running on that cpu.
With this patch del_timer_sync is O(1) and no slower than plain
del_timer(pending_timer), unless it has to actually wait for
completion of the currently running timer.
The only restriction is that the recurring timer should not use
add_timer_on().
3. The timers are not serialized wrt to itself.
If CPU_0 does mod_timer(jiffies+1) while the timer is currently
running on CPU 1, it is quite possible that local interrupt on
CPU_0 will start that timer before it finished on CPU_1.
4. The timers locking is suboptimal. __mod_timer() takes 3 locks
at once and still requires wmb() in del_timer/run_timers.
The new implementation takes 2 locks sequentially and does not
need memory barriers.
Currently ->base != NULL means that the timer is pending. In that case
->base.lock is used to lock the timer. __mod_timer also takes timer->lock
because ->base can be == NULL.
This patch uses timer->entry.next != NULL as indication that the timer is
pending. So it does __list_del(), entry->next = NULL instead of list_del()
when the timer is deleted.
The ->base field is used for hashed locking only, it is initialized
in init_timer() which sets ->base = per_cpu(tvec_bases). When the
tvec_bases.lock is locked, it means that all timers which are tied
to this base via timer->base are locked, and the base itself is locked
too.
So __run_timers/migrate_timers can safely modify all timers which could
be found on ->tvX lists (pending timers).
When the timer's base is locked, and the timer removed from ->entry list
(which means that _run_timers/migrate_timers can't see this timer), it is
possible to set timer->base = NULL and drop the lock: the timer remains
locked.
This patch adds lock_timer_base() helper, which waits for ->base != NULL,
locks the ->base, and checks it is still the same.
__mod_timer() schedules the timer on the local CPU and changes it's base.
However, it does not lock both old and new bases at once. It locks the
timer via lock_timer_base(), deletes the timer, sets ->base = NULL, and
unlocks old base. Then __mod_timer() locks new_base, sets ->base = new_base,
and adds this timer. This simplifies the code, because AB-BA deadlock is not
possible. __mod_timer() also ensures that the timer's base is not changed
while the timer's handler is running on the old base.
__run_timers(), del_timer() do not change ->base anymore, they only clear
pending flag.
So del_timer_sync() can test timer->base->running_timer == timer to detect
whether it is running or not.
We don't need timer_list->lock anymore, this patch kills it.
We also don't need barriers. del_timer() and __run_timers() used smp_wmb()
before clearing timer's pending flag. It was needed because __mod_timer()
did not lock old_base if the timer is not pending, so __mod_timer()->list_add()
could race with del_timer()->list_del(). With this patch these functions are
serialized through base->lock.
One problem. TIMER_INITIALIZER can't use per_cpu(tvec_bases). So this patch
adds global
struct timer_base_s {
spinlock_t lock;
struct timer_list *running_timer;
} __init_timer_base;
which is used by TIMER_INITIALIZER. The corresponding fields in tvec_t_base_s
struct are replaced by struct timer_base_s t_base.
It is indeed ugly. But this can't have scalability problems. The global
__init_timer_base.lock is used only when __mod_timer() is called for the first
time AND the timer was compile time initialized. After that the timer migrates
to the local CPU.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Renaud Lienhart <renaud.lienhart@free.fr>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-23 14:08:56 +07:00
|
|
|
migrate_timer_list(new_base, old_base->tv1.vec + i);
|
|
|
|
for (i = 0; i < TVN_SIZE; i++) {
|
|
|
|
migrate_timer_list(new_base, old_base->tv2.vec + i);
|
|
|
|
migrate_timer_list(new_base, old_base->tv3.vec + i);
|
|
|
|
migrate_timer_list(new_base, old_base->tv4.vec + i);
|
|
|
|
migrate_timer_list(new_base, old_base->tv5.vec + i);
|
|
|
|
}
|
|
|
|
|
2008-04-05 01:54:10 +07:00
|
|
|
spin_unlock(&old_base->lock);
|
2008-08-21 06:46:04 +07:00
|
|
|
spin_unlock_irq(&new_base->lock);
|
2005-04-17 05:20:36 +07:00
|
|
|
put_cpu_var(tvec_bases);
|
|
|
|
}
|
|
|
|
#endif /* CONFIG_HOTPLUG_CPU */
|
|
|
|
|
2013-06-20 01:53:51 +07:00
|
|
|
static int timer_cpu_notify(struct notifier_block *self,
|
2005-04-17 05:20:36 +07:00
|
|
|
unsigned long action, void *hcpu)
|
|
|
|
{
|
|
|
|
long cpu = (long)hcpu;
|
2010-05-27 04:43:32 +07:00
|
|
|
int err;
|
|
|
|
|
2005-04-17 05:20:36 +07:00
|
|
|
switch(action) {
|
|
|
|
case CPU_UP_PREPARE:
|
2007-05-09 16:35:10 +07:00
|
|
|
case CPU_UP_PREPARE_FROZEN:
|
2010-05-27 04:43:32 +07:00
|
|
|
err = init_timers_cpu(cpu);
|
|
|
|
if (err < 0)
|
|
|
|
return notifier_from_errno(err);
|
2005-04-17 05:20:36 +07:00
|
|
|
break;
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
|
|
case CPU_DEAD:
|
2007-05-09 16:35:10 +07:00
|
|
|
case CPU_DEAD_FROZEN:
|
2005-04-17 05:20:36 +07:00
|
|
|
migrate_timers(cpu);
|
|
|
|
break;
|
|
|
|
#endif
|
|
|
|
default:
|
|
|
|
break;
|
|
|
|
}
|
|
|
|
return NOTIFY_OK;
|
|
|
|
}
|
|
|
|
|
2013-06-20 01:53:51 +07:00
|
|
|
static struct notifier_block timers_nb = {
|
2005-04-17 05:20:36 +07:00
|
|
|
.notifier_call = timer_cpu_notify,
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
|
|
void __init init_timers(void)
|
|
|
|
{
|
2012-08-09 01:10:25 +07:00
|
|
|
int err;
|
|
|
|
|
|
|
|
/* ensure there are enough low bits for flags in timer->base pointer */
|
|
|
|
BUILD_BUG_ON(__alignof__(struct tvec_base) & TIMER_FLAG_MASK);
|
2006-09-29 16:00:22 +07:00
|
|
|
|
2012-08-09 01:10:25 +07:00
|
|
|
err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
|
|
|
|
(void *)(long)smp_processor_id());
|
2010-06-05 04:15:04 +07:00
|
|
|
BUG_ON(err != NOTIFY_OK);
|
2014-02-28 15:45:21 +07:00
|
|
|
|
|
|
|
init_timer_stats();
|
2005-04-17 05:20:36 +07:00
|
|
|
register_cpu_notifier(&timers_nb);
|
Remove argument from open_softirq which is always NULL
As git-grep shows, open_softirq() is always called with the last argument
being NULL
block/blk-core.c: open_softirq(BLOCK_SOFTIRQ, blk_done_softirq, NULL);
kernel/hrtimer.c: open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL);
kernel/rcuclassic.c: open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
kernel/rcupreempt.c: open_softirq(RCU_SOFTIRQ, rcu_process_callbacks, NULL);
kernel/sched.c: open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);
kernel/softirq.c: open_softirq(TASKLET_SOFTIRQ, tasklet_action, NULL);
kernel/softirq.c: open_softirq(HI_SOFTIRQ, tasklet_hi_action, NULL);
kernel/timer.c: open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL);
net/core/dev.c: open_softirq(NET_TX_SOFTIRQ, net_tx_action, NULL);
net/core/dev.c: open_softirq(NET_RX_SOFTIRQ, net_rx_action, NULL);
This observation has already been made by Matthew Wilcox in June 2002
(http://www.cs.helsinki.fi/linux/linux-kernel/2002-25/0687.html)
"I notice that none of the current softirq routines use the data element
passed to them."
and the situation hasn't changed since them. So it appears we can safely
remove that extra argument to save 128 (54) bytes of kernel data (text).
Signed-off-by: Carlos R. Mafra <crmafra@ift.unesp.br>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-05-15 21:15:37 +07:00
|
|
|
open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
|
|
* msleep - sleep safely even with waitqueue interruptions
|
|
|
|
* @msecs: Time in milliseconds to sleep for
|
|
|
|
*/
|
|
|
|
void msleep(unsigned int msecs)
|
|
|
|
{
|
|
|
|
unsigned long timeout = msecs_to_jiffies(msecs) + 1;
|
|
|
|
|
2005-09-10 14:27:24 +07:00
|
|
|
while (timeout)
|
|
|
|
timeout = schedule_timeout_uninterruptible(timeout);
|
2005-04-17 05:20:36 +07:00
|
|
|
}
|
|
|
|
|
|
|
|
EXPORT_SYMBOL(msleep);
|
|
|
|
|
|
|
|
/**
|
2005-06-26 04:58:43 +07:00
|
|
|
* msleep_interruptible - sleep waiting for signals
|
2005-04-17 05:20:36 +07:00
|
|
|
* @msecs: Time in milliseconds to sleep for
|
|
|
|
*/
|
|
|
|
unsigned long msleep_interruptible(unsigned int msecs)
|
|
|
|
{
|
|
|
|
unsigned long timeout = msecs_to_jiffies(msecs) + 1;
|
|
|
|
|
2005-09-10 14:27:24 +07:00
|
|
|
while (timeout && !signal_pending(current))
|
|
|
|
timeout = schedule_timeout_interruptible(timeout);
|
2005-04-17 05:20:36 +07:00
|
|
|
return jiffies_to_msecs(timeout);
|
|
|
|
}
|
|
|
|
|
|
|
|
EXPORT_SYMBOL(msleep_interruptible);
|
timer: Added usleep_range timer
usleep_range is a finer precision implementations of msleep
and is designed to be a drop-in replacement for udelay where
a precise sleep / busy-wait is unnecessary.
Since an easy interface to hrtimers could lead to an undesired
proliferation of interrupts, we provide only a "range" API,
forcing the caller to think about an acceptable tolerance on
both ends and hopefully avoiding introducing another interrupt.
INTRO
As discussed here ( http://lkml.org/lkml/2007/8/3/250 ), msleep(1) is not
precise enough for many drivers (yes, sleep precision is an unfair notion,
but consistently sleeping for ~an order of magnitude greater than requested
is worth fixing). This patch adds a usleep API so that udelay does not have
to be used. Obviously not every udelay can be replaced (those in atomic
contexts or being used for simple bitbanging come to mind), but there are
many, many examples of
mydriver_write(...)
/* Wait for hardware to latch */
udelay(100)
in various drivers where a busy-wait loop is neither beneficial nor
necessary, but msleep simply does not provide enough precision and people
are using a busy-wait loop instead.
CONCERNS FROM THE RFC
Why is udelay a problem / necessary? Most callers of udelay are in device/
driver initialization code, which is serial...
As I see it, there is only benefit to sleeping over a delay; the
notion of "refactoring" areas that use udelay was presented, but
I see usleep as the refactoring. Consider i2c, if the bus is busy,
you need to wait a bit (say 100us) before trying again, your
current options are:
* udelay(100)
* msleep(1) <-- As noted above, actually as high as ~20ms
on some platforms, so not really an option
* Manually set up an hrtimer to try again in 100us (which
is what usleep does anyway...)
People choose the udelay route because it is EASY; we need to
provide a better easy route.
Device / driver / boot code is *currently* serial, but every few
months someone makes noise about parallelizing boot, and IMHO, a
little forward-thinking now is one less thing to worry about
if/when that ever happens
udelay's could be preempted
Sure, but if udelay plans on looping 1000 times, and it gets
preempted on loop 200, whenever it's scheduled again, it is
going to do the next 800 loops.
Is the interruptible case needed?
Probably not, but I see usleep as a very logical parallel to msleep,
so it made sense to include the "full" API. Processors are getting
faster (albeit not as quickly as they are becoming more parallel),
so if someone wanted to be interruptible for a few usecs, why not
let them? If this is a contentious point, I'm happy to remove it.
OTHER THOUGHTS
I believe there is also value in exposing the usleep_range option; it gives
the scheduler a lot more flexibility and allows the programmer to express
his intent much more clearly; it's something I would hope future driver
writers will take advantage of.
To get the results in the NUMBERS section below, I literally s/udelay/usleep
the kernel tree; I had to go in and undo the changes to the USB drivers, but
everything else booted successfully; I find that extremely telling in and
of itself -- many people are using a delay API where a sleep will suit them
just fine.
SOME ATTEMPTS AT NUMBERS
It turns out that calculating quantifiable benefit on this is challenging,
so instead I will simply present the current state of things, and I hope
this to be sufficient:
How many udelay calls are there in 2.6.35-rc5?
udealy(ARG) >= | COUNT
1000 | 319
500 | 414
100 | 1146
20 | 1832
I am working on Android, so that is my focus for this. The following table
is a modified usleep that simply printk's the amount of time requested to
sleep; these tests were run on a kernel with udelay >= 20 --> usleep
"boot" is power-on to lock screen
"power collapse" is when the power button is pushed and the device suspends
"resume" is when the power button is pushed and the lock screen is displayed
(no touchscreen events or anything, just turning on the display)
"use device" is from the unlock swipe to clicking around a bit; there is no
sd card in this phone, so fail loading music, video, camera
ACTION | TOTAL NUMBER OF USLEEP CALLS | NET TIME (us)
boot | 22 | 1250
power-collapse | 9 | 1200
resume | 5 | 500
use device | 59 | 7700
The most interesting category to me is the "use device" field; 7700us of
busy-wait time that could be put towards better responsiveness, or at the
least less power usage.
Signed-off-by: Patrick Pannuto <ppannuto@codeaurora.org>
Cc: apw@canonical.com
Cc: corbet@lwn.net
Cc: arjan@linux.intel.com
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2010-08-03 05:01:04 +07:00
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static int __sched do_usleep_range(unsigned long min, unsigned long max)
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{
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ktime_t kmin;
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unsigned long delta;
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kmin = ktime_set(0, min * NSEC_PER_USEC);
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delta = (max - min) * NSEC_PER_USEC;
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return schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
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}
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/**
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* usleep_range - Drop in replacement for udelay where wakeup is flexible
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* @min: Minimum time in usecs to sleep
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* @max: Maximum time in usecs to sleep
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*/
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void usleep_range(unsigned long min, unsigned long max)
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{
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__set_current_state(TASK_UNINTERRUPTIBLE);
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do_usleep_range(min, max);
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}
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EXPORT_SYMBOL(usleep_range);
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