Commit Graph

1347 Commits

Author SHA1 Message Date
John Stultz
58bfea9532 timekeeping: Fix __ktime_get_fast_ns() regression
In commit 27727df240 ("Avoid taking lock in NMI path with
CONFIG_DEBUG_TIMEKEEPING"), I changed the logic to open-code
the timekeeping_get_ns() function, but I forgot to include
the unit conversion from cycles to nanoseconds, breaking the
function's output, which impacts users like perf.

This results in bogus perf timestamps like:
 swapper     0 [000]   253.427536:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.426573:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.426687:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.426800:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.426905:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427022:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427127:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427239:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427346:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   254.427463:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]   255.426572:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])

Instead of more reasonable expected timestamps like:
 swapper     0 [000]    39.953768:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.064839:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.175956:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.287103:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.398217:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.509324:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.620437:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.731546:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.842654:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    40.953772:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])
 swapper     0 [000]    41.064881:  111111111 cpu-clock:  ffffffff810a0de6 native_safe_halt+0x6 ([kernel.kallsyms])

Add the proper use of timekeeping_delta_to_ns() to convert
the cycle delta to nanoseconds as needed.

Thanks to Brendan and Alexei for finding this quickly after
the v4.8 release. Unfortunately the problematic commit has
landed in some -stable trees so they'll need this fix as
well.

Many apologies for this mistake. I'll be looking to add a
perf-clock sanity test to the kselftest timers tests soon.

Fixes: 27727df240 "timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING"
Reported-by: Brendan Gregg <bgregg@netflix.com>
Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Tested-and-reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable <stable@vger.kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1475636148-26539-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-10-05 15:44:46 +02:00
Wanpeng Li
57ccdf449f tick/nohz: Prevent stopping the tick on an offline CPU
can_stop_full_tick() has no check for offline cpus. So it allows to stop
the tick on an offline cpu from the interrupt return path, which is wrong
and subsequently makes irq_work_needs_cpu() warn about being called for an
offline cpu.

Commit f7ea0fd639 ("tick: Don't invoke tick_nohz_stop_sched_tick() if
the cpu is offline") added prevention for can_stop_idle_tick(), but forgot
to do the same in can_stop_full_tick(). Add it.

[ tglx: Massaged changelog ]

Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1473245473-4463-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-09-13 17:53:52 +02:00
Ingo Molnar
950d8381d9 Merge branch 'linus' into timers/core, to refresh the branch
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-09-08 14:05:16 +02:00
Wanpeng Li
08d0725992 tick/nohz: Fix softlockup on scheduler stalls in kvm guest
tick_nohz_start_idle() is prevented to be called if the idle tick can't 
be stopped since commit 1f3b0f8243 ("tick/nohz: Optimize nohz idle 
enter"). As a result, after suspend/resume the host machine, full dynticks 
kvm guest will softlockup:

 NMI watchdog: BUG: soft lockup - CPU#0 stuck for 26s! [swapper/0:0]
 Call Trace:
  default_idle+0x31/0x1a0
  arch_cpu_idle+0xf/0x20
  default_idle_call+0x2a/0x50
  cpu_startup_entry+0x39b/0x4d0
  rest_init+0x138/0x140
  ? rest_init+0x5/0x140
  start_kernel+0x4c1/0x4ce
  ? set_init_arg+0x55/0x55
  ? early_idt_handler_array+0x120/0x120
  x86_64_start_reservations+0x24/0x26
  x86_64_start_kernel+0x142/0x14f

In addition, cat /proc/stat | grep cpu in guest or host:

cpu  398 16 5049 15754 5490 0 1 46 0 0
cpu0 206 5 450 0 0 0 1 14 0 0
cpu1 81 0 3937 3149 1514 0 0 9 0 0
cpu2 45 6 332 6052 2243 0 0 11 0 0
cpu3 65 2 328 6552 1732 0 0 11 0 0

The idle and iowait states are weird 0 for cpu0(housekeeping). 

The bug is present in both guest and host kernels, and they both have 
cpu0's idle and iowait states issue, however, host kernel's suspend/resume 
path etc will touch watchdog to avoid the softlockup.

- The watchdog will not be touched in tick_nohz_stop_idle path (need be 
  touched since the scheduler stall is expected) if idle_active flags are 
  not detected.
- The idle and iowait states will not be accounted when exit idle loop 
  (resched or interrupt) if idle start time and idle_active flags are 
  not set. 

This patch fixes it by reverting commit 1f3b0f8243 since can't stop 
idle tick doesn't mean can't be idle.

Fixes: 1f3b0f8243 ("tick/nohz: Optimize nohz idle enter")
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Sanjeev Yadav<sanjeev.yadav@spreadtrum.com>
Cc: Gaurav Jindal<gaurav.jindal@spreadtrum.com>
Cc: stable@vger.kernel.org
Cc: kvm@vger.kernel.org
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: http://lkml.kernel.org/r/1472798303-4154-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-09-02 10:25:40 +02:00
Vegard Nossum
979515c564 time: Avoid undefined behaviour in ktime_add_safe()
I ran into this:

    ================================================================================
    UBSAN: Undefined behaviour in kernel/time/hrtimer.c:310:16
    signed integer overflow:
    9223372036854775807 + 50000 cannot be represented in type 'long long int'
    CPU: 2 PID: 4798 Comm: trinity-c2 Not tainted 4.8.0-rc1+ #91
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014
     0000000000000000 ffff88010ce6fb88 ffffffff82344740 0000000041b58ab3
     ffffffff84f97a20 ffffffff82344694 ffff88010ce6fbb0 ffff88010ce6fb60
     000000000000c350 ffff88010ce6f968 dffffc0000000000 ffffffff857bc320
    Call Trace:
     [<ffffffff82344740>] dump_stack+0xac/0xfc
     [<ffffffff82344694>] ? _atomic_dec_and_lock+0xc4/0xc4
     [<ffffffff8242df78>] ubsan_epilogue+0xd/0x8a
     [<ffffffff8242e6b4>] handle_overflow+0x202/0x23d
     [<ffffffff8242e4b2>] ? val_to_string.constprop.6+0x11e/0x11e
     [<ffffffff8236df71>] ? timerqueue_add+0x151/0x410
     [<ffffffff81485c48>] ? hrtimer_start_range_ns+0x3b8/0x1380
     [<ffffffff81795631>] ? memset+0x31/0x40
     [<ffffffff8242e6fd>] __ubsan_handle_add_overflow+0xe/0x10
     [<ffffffff81488ac9>] hrtimer_nanosleep+0x5d9/0x790
     [<ffffffff814884f0>] ? hrtimer_init_sleeper+0x80/0x80
     [<ffffffff813a9ffb>] ? __might_sleep+0x5b/0x260
     [<ffffffff8148be10>] common_nsleep+0x20/0x30
     [<ffffffff814906c7>] SyS_clock_nanosleep+0x197/0x210
     [<ffffffff81490530>] ? SyS_clock_getres+0x150/0x150
     [<ffffffff823c7113>] ? __this_cpu_preempt_check+0x13/0x20
     [<ffffffff8162ef60>] ? __context_tracking_exit.part.3+0x30/0x1b0
     [<ffffffff81490530>] ? SyS_clock_getres+0x150/0x150
     [<ffffffff81007bd3>] do_syscall_64+0x1b3/0x4b0
     [<ffffffff845f85aa>] entry_SYSCALL64_slow_path+0x25/0x25
    ================================================================================

Add a new ktime_add_unsafe() helper which doesn't check for overflow, but
doesn't throw a UBSAN warning when it does overflow either.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-08-31 14:43:36 -07:00
Vegard Nossum
469e857f37 time: Avoid undefined behaviour in timespec64_add_safe()
I ran into this:

    ================================================================================
    UBSAN: Undefined behaviour in kernel/time/time.c:783:2
    signed integer overflow:
    5273 + 9223372036854771711 cannot be represented in type 'long int'
    CPU: 0 PID: 17363 Comm: trinity-c0 Not tainted 4.8.0-rc1+ #88
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org
    04/01/2014
     0000000000000000 ffff88011457f8f0 ffffffff82344f50 0000000041b58ab3
     ffffffff84f98080 ffffffff82344ea4 ffff88011457f918 ffff88011457f8c8
     ffff88011457f8e0 7fffffffffffefff ffff88011457f6d8 dffffc0000000000
    Call Trace:
     [<ffffffff82344f50>] dump_stack+0xac/0xfc
     [<ffffffff82344ea4>] ? _atomic_dec_and_lock+0xc4/0xc4
     [<ffffffff8242f4c8>] ubsan_epilogue+0xd/0x8a
     [<ffffffff8242fc04>] handle_overflow+0x202/0x23d
     [<ffffffff8242fa02>] ? val_to_string.constprop.6+0x11e/0x11e
     [<ffffffff823c7837>] ? debug_smp_processor_id+0x17/0x20
     [<ffffffff8131b581>] ? __sigqueue_free.part.13+0x51/0x70
     [<ffffffff8146d4e0>] ? rcu_is_watching+0x110/0x110
     [<ffffffff8242fc4d>] __ubsan_handle_add_overflow+0xe/0x10
     [<ffffffff81476ef8>] timespec64_add_safe+0x298/0x340
     [<ffffffff81476c60>] ? timespec_add_safe+0x330/0x330
     [<ffffffff812f7990>] ? wait_noreap_copyout+0x1d0/0x1d0
     [<ffffffff8184bf18>] poll_select_set_timeout+0xf8/0x170
     [<ffffffff8184be20>] ? poll_schedule_timeout+0x2b0/0x2b0
     [<ffffffff813aa9bb>] ? __might_sleep+0x5b/0x260
     [<ffffffff833c8a87>] __sys_recvmmsg+0x107/0x790
     [<ffffffff833c8980>] ? SyS_recvmsg+0x20/0x20
     [<ffffffff81486378>] ? hrtimer_start_range_ns+0x3b8/0x1380
     [<ffffffff845f8bfb>] ? _raw_spin_unlock_irqrestore+0x3b/0x60
     [<ffffffff8148bcea>] ? do_setitimer+0x39a/0x8e0
     [<ffffffff813aa9bb>] ? __might_sleep+0x5b/0x260
     [<ffffffff833c9110>] ? __sys_recvmmsg+0x790/0x790
     [<ffffffff833c91e9>] SyS_recvmmsg+0xd9/0x160
     [<ffffffff833c9110>] ? __sys_recvmmsg+0x790/0x790
     [<ffffffff823c7853>] ? __this_cpu_preempt_check+0x13/0x20
     [<ffffffff8162f680>] ? __context_tracking_exit.part.3+0x30/0x1b0
     [<ffffffff833c9110>] ? __sys_recvmmsg+0x790/0x790
     [<ffffffff81007bd3>] do_syscall_64+0x1b3/0x4b0
     [<ffffffff845f936a>] entry_SYSCALL64_slow_path+0x25/0x25
    ================================================================================

Line 783 is this:

783         set_normalized_timespec64(&res, lhs.tv_sec + rhs.tv_sec,
784                         lhs.tv_nsec + rhs.tv_nsec);

In other words, since lhs.tv_sec and rhs.tv_sec are both time64_t, this
is a signed addition which will cause undefined behaviour on overflow.

Note that this is not currently a huge concern since the kernel should be
built with -fno-strict-overflow by default, but could be a problem in the
future, a problem with older compilers, or other compilers than gcc.

The easiest way to avoid the overflow is to cast one of the arguments to
unsigned (so the addition will be done using unsigned arithmetic).

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-08-31 14:43:35 -07:00
Ruchi Kandoi
0bf43f15db timekeeping: Prints the amounts of time spent during suspend
In addition to keeping a histogram of suspend times, also
print out the time spent in suspend to dmesg.

This helps to keep track of suspend time while debugging using
kernel logs.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>
[jstultz: Tweaked commit message]
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-08-31 14:43:34 -07:00
Kyle Walker
36374583f9 clocksource: Defer override invalidation unless clock is unstable
Clocksources don't get the VALID_FOR_HRES flag until they have been
checked by a watchdog. However, when using an override, the
clocksource_select logic will clear the override value if the
clocksource is not marked VALID_FOR_HRES during that inititial check.
When using the boot arguments clocksource=<foo>, this selection can
run before the watchdog, and can cause the override to be incorrectly
cleared.

To address this condition, the override_name is only invalidated for
unstable clocksources. Otherwise, the override is left intact until after
the watchdog has validated the clocksource as stable/unstable.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Kyle Walker <kwalker@redhat.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-08-31 14:43:33 -07:00
Pratyush Patel
b4d90e9f1e hrtimer: Spelling fixes
Fix a minor spelling error.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Pratyush Patel <pratyushpatel.1995@gmail.com>
[jstultz: Added commit message]
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-08-31 14:43:20 -07:00
John Stultz
a4f8f6667f timekeeping: Cap array access in timekeeping_debug
It was reported that hibernation could fail on the 2nd attempt, where the
system hangs at hibernate() -> syscore_resume() -> i8237A_resume() ->
claim_dma_lock(), because the lock has already been taken.

However there is actually no other process would like to grab this lock on
that problematic platform.

Further investigation showed that the problem is triggered by setting
/sys/power/pm_trace to 1 before the 1st hibernation.

Since once pm_trace is enabled, the rtc becomes unmeaningful after suspend,
and meanwhile some BIOSes would like to adjust the 'invalid' RTC (e.g, smaller
than 1970) to the release date of that motherboard during POST stage, thus
after resumed, it may seem that the system had a significant long sleep time
which is a completely meaningless value.

Then in timekeeping_resume -> tk_debug_account_sleep_time, if the bit31 of the
sleep time happened to be set to 1, fls() returns 32 and we add 1 to
sleep_time_bin[32], which causes an out of bounds array access and therefor
memory being overwritten.

As depicted by System.map:
0xffffffff81c9d080 b sleep_time_bin
0xffffffff81c9d100 B dma_spin_lock
the dma_spin_lock.val is set to 1, which caused this problem.

This patch adds a sanity check in tk_debug_account_sleep_time()
to ensure we don't index past the sleep_time_bin array.

[jstultz: Problem diagnosed and original patch by Chen Yu, I've solved the
 issue slightly differently, but borrowed his excelent explanation of the
 issue here.]

Fixes: 5c83545f24 "power: Add option to log time spent in suspend"
Reported-by: Janek Kozicki <cosurgi@gmail.com>
Reported-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: linux-pm@vger.kernel.org
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xunlei Pang <xpang@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: stable <stable@vger.kernel.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Link: http://lkml.kernel.org/r/1471993702-29148-3-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-08-24 09:34:32 +02:00
John Stultz
27727df240 timekeeping: Avoid taking lock in NMI path with CONFIG_DEBUG_TIMEKEEPING
When I added some extra sanity checking in timekeeping_get_ns() under
CONFIG_DEBUG_TIMEKEEPING, I missed that the NMI safe __ktime_get_fast_ns()
method was using timekeeping_get_ns().

Thus the locking added to the debug checks broke the NMI-safety of
__ktime_get_fast_ns().

This patch open-codes the timekeeping_get_ns() logic for
__ktime_get_fast_ns(), so can avoid any deadlocks in NMI.

Fixes: 4ca22c2648 "timekeeping: Add warnings when overflows or underflows are observed"
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: stable <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/1471993702-29148-2-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-08-24 09:34:31 +02:00
Chris Metcalf
46c8f0b077 timers: Fix get_next_timer_interrupt() computation
The tick_nohz_stop_sched_tick() routine is not properly
canceling the sched timer when nothing is pending, because
get_next_timer_interrupt() is no longer returning KTIME_MAX in
that case.  This causes periodic interrupts when none are needed.

When determining the next interrupt time, we first use
__next_timer_interrupt() to get the first expiring timer in the
timer wheel.  If no timer is found, we return the base clock value
plus NEXT_TIMER_MAX_DELTA to indicate there is no timer in the
timer wheel.

Back in get_next_timer_interrupt(), we set the "expires" value
by converting the timer wheel expiry (in ticks) to a nsec value.
But we don't want to do this if the timer wheel expiry value
indicates no timer; we want to return KTIME_MAX.

Prior to commit 500462a9de ("timers: Switch to a non-cascading
wheel") we checked base->active_timers to see if any timers
were active, and if not, we didn't touch the expiry value and so
properly returned KTIME_MAX.  Now we don't have active_timers.

To fix this, we now just check the timer wheel expiry value to
see if it is "now + NEXT_TIMER_MAX_DELTA", and if it is, we don't
try to compute a new value based on it, but instead simply let the
KTIME_MAX value in expires remain.

Fixes: 500462a9de "timers: Switch to a non-cascading wheel"
Signed-off-by: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/1470688147-22287-1-git-send-email-cmetcalf@mellanox.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-08-09 09:31:55 +02:00
Linus Torvalds
a6408f6cb6 Merge branch 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull smp hotplug updates from Thomas Gleixner:
 "This is the next part of the hotplug rework.

   - Convert all notifiers with a priority assigned

   - Convert all CPU_STARTING/DYING notifiers

     The final removal of the STARTING/DYING infrastructure will happen
     when the merge window closes.

  Another 700 hundred line of unpenetrable maze gone :)"

* 'smp-hotplug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  timers/core: Correct callback order during CPU hot plug
  leds/trigger/cpu: Move from CPU_STARTING to ONLINE level
  powerpc/numa: Convert to hotplug state machine
  arm/perf: Fix hotplug state machine conversion
  irqchip/armada: Avoid unused function warnings
  ARC/time: Convert to hotplug state machine
  clocksource/atlas7: Convert to hotplug state machine
  clocksource/armada-370-xp: Convert to hotplug state machine
  clocksource/exynos_mct: Convert to hotplug state machine
  clocksource/arm_global_timer: Convert to hotplug state machine
  rcu: Convert rcutree to hotplug state machine
  KVM/arm/arm64/vgic-new: Convert to hotplug state machine
  smp/cfd: Convert core to hotplug state machine
  x86/x2apic: Convert to CPU hotplug state machine
  profile: Convert to hotplug state machine
  timers/core: Convert to hotplug state machine
  hrtimer: Convert to hotplug state machine
  x86/tboot: Convert to hotplug state machine
  arm64/armv8 deprecated: Convert to hotplug state machine
  hwtracing/coresight-etm4x: Convert to hotplug state machine
  ...
2016-07-29 13:55:30 -07:00
Linus Torvalds
55392c4c06 Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
 "This update provides the following changes:

   - The rework of the timer wheel which addresses the shortcomings of
     the current wheel (cascading, slow search for next expiring timer,
     etc).  That's the first major change of the wheel in almost 20
     years since Finn implemted it.

   - A large overhaul of the clocksource drivers init functions to
     consolidate the Device Tree initialization

   - Some more Y2038 updates

   - A capability fix for timerfd

   - Yet another clock chip driver

   - The usual pile of updates, comment improvements all over the place"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (130 commits)
  tick/nohz: Optimize nohz idle enter
  clockevents: Make clockevents_subsys static
  clocksource/drivers/time-armada-370-xp: Fix return value check
  timers: Implement optimization for same expiry time in mod_timer()
  timers: Split out index calculation
  timers: Only wake softirq if necessary
  timers: Forward the wheel clock whenever possible
  timers/nohz: Remove pointless tick_nohz_kick_tick() function
  timers: Optimize collect_expired_timers() for NOHZ
  timers: Move __run_timers() function
  timers: Remove set_timer_slack() leftovers
  timers: Switch to a non-cascading wheel
  timers: Reduce the CPU index space to 256k
  timers: Give a few structs and members proper names
  hlist: Add hlist_is_singular_node() helper
  signals: Use hrtimer for sigtimedwait()
  timers: Remove the deprecated mod_timer_pinned() API
  timers, net/ipv4/inet: Initialize connection request timers as pinned
  timers, drivers/tty/mips_ejtag: Initialize the poll timer as pinned
  timers, drivers/tty/metag_da: Initialize the poll timer as pinned
  ...
2016-07-25 20:43:12 -07:00
Linus Torvalds
25a0dc4be8 Staging / IIO driver update for 4.8-rc1
Here is the big Staging and IIO driver update for 4.8-rc1.
 
 We ended up adding more code than removing, again, but it's not all that
 bad.  Lots of cleanups all over the staging tree, and new IIO drivers,
 full details in the shortlog.
 
 All of these have been in linux-next for a while with no reported issues.
 
 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'staging-4.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

Pull staging and IIO driver updates from Greg KH:
 "Here is the big Staging and IIO driver update for 4.8-rc1.

  We ended up adding more code than removing, again, but it's not all
  that bad.  Lots of cleanups all over the staging tree, and new IIO
  drivers, full details in the shortlog.

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'staging-4.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging: (417 commits)
  drivers:iio:accel:mma8452: removed unwanted return statements
  drivers:iio:accel:mma8452: added cleanup provision in case of failure.
  iio: Add iio.git tree to MAINTAINERS
  iio:st_pressure: clean useless static channel initializers
  iio:st_pressure:lps22hb: temperature support
  iio:st_pressure:lps22hb: open drain support
  iio:st_pressure: temperature triggered buffering
  iio:st_pressure: document sampling gains
  iio:st_pressure: align storagebits on power of 2
  iio:st_sensors: align on storagebits boundaries
  staging:iio:lis3l02dq drop separate driver
  iio: accel: st_accel: Add lis3l02dq support
  iio: adc: add missing of_node references to iio_dev
  iio: adc: ti-ads1015: add indio_dev->dev.of_node reference
  iio: potentiometer: Fix typo in Kconfig
  iio: potentiometer: mcp4531: Add device tree binding
  iio: potentiometer: mcp4531: Add device tree binding documentation
  iio: potentiometer: mcp4531: Add support for MCP454x, MCP456x, MCP464x and MCP466x
  iio:imu:mpu6050: icm20608 initial support
  iio: adc: max1363: Add device tree binding
  ...
2016-07-24 16:55:23 -07:00
Gaurav Jindal
1f3b0f8243 tick/nohz: Optimize nohz idle enter
tick_nohz_start_idle is called before checking whether the idle tick can be
stopped. If the tick cannot be stopped, calling tick_nohz_start_idle() is
pointless and just wasting CPU cycles.

Only invoke tick_nohz_start_idle() when can_stop_idle_tick() returns true. A
short one minute observation of the effect on ARM64 shows a reduction of calls
by 1.5% thus optimizing the idle entry sequence.

[tglx: Massaged changelog ]

Co-developed-by: Sanjeev Yadav<sanjeev.yadav@spreadtrum.com>
Signed-off-by: Gaurav Jindal<gaurav.jindal@spreadtrum.com>
Link: http://lkml.kernel.org/r/20160714120416.GB21099@gaurav.jindal@spreadtrum.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-07-19 13:48:24 +02:00
Ben Dooks
775be50626 clockevents: Make clockevents_subsys static
The clockevents_subsys struct is used for sysfs support and
is not declared or used outside the file it is defined in.
Fix the following warning by making it static:

kernel/time/clockevents.c:648:17: warning: symbol 'clockevents_subsys' was not declared. Should it be static?

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Cc: linux-kernel@lists.codethink.co.uk
Link: http://lkml.kernel.org/r/1466178974-7105-1-git-send-email-ben.dooks@codethink.co.uk
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-07-19 10:48:06 +02:00
Richard Cochran
24f73b9971 timers/core: Convert to hotplug state machine
When tearing down, call timers_dead_cpu() before notify_dead().
There is a hidden dependency between:

 - timers
 - block multiqueue
 - rcutree

If timers_dead_cpu() comes later than blk_mq_queue_reinit_notify()
that latter function causes a RCU stall.

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153337.566790058@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-15 10:41:42 +02:00
Thomas Gleixner
27590dc17b hrtimer: Convert to hotplug state machine
Split out the clockevents callbacks instead of piggybacking them on
hrtimers.

This gets rid of a POST_DEAD user. See commit:

  54e88fad22 ("sched: Make sure timers have migrated before killing the migration_thread")

We just move the callback state to the proper place in the state machine.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153337.485419196@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-15 10:41:37 +02:00
Alexey Dobriyan
2c13ce8f6b posix_cpu_timer: Exit early when process has been reaped
Variable "now" seems to be genuinely used unintialized
if branch

	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {

is not taken and branch

	if (unlikely(sighand == NULL)) {

is taken. In this case the process has been reaped and the timer is marked as
disarmed anyway. So none of the postprocessing of the sample is
required. Return right away.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20160707223911.GA26483@p183.telecom.by
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-07-11 17:20:12 +02:00
Ingo Molnar
4b4b20852d Merge branch 'timers/fast-wheel' into timers/core 2016-07-07 10:35:28 +02:00
Anna-Maria Gleixner
f00c0afdfa timers: Implement optimization for same expiry time in mod_timer()
The existing optimization for same expiry time in mod_timer() checks whether
the timer expiry time is the same as the new requested expiry time. In the old
timer wheel implementation this does not take the slack batching into account,
neither does the new implementation evaluate whether the new expiry time will
requeue the timer to the same bucket.

To optimize that, we can calculate the resulting bucket and check if the new
expiry time is different from the current expiry time. This calculation
happens outside the base lock held region. If the resulting bucket is the same
we can avoid taking the base lock and requeueing the timer.

If the timer needs to be requeued then we have to check under the base lock
whether the base time has changed between the lockless calculation and taking
the lock. If it has changed we need to recalculate under the lock.

This optimization takes effect for timers which are enqueued into the less
granular wheel levels (1 and above). With a simple test case the functionality
has been verified:

            Before        After
 Match:       5.5%        86.6%
 Requeue:    94.5%        13.4%
 Recalc:                  <0.01%

In the non optimized case the timer is requeued in 94.5% of the cases. With
the index optimization in place the requeue rate drops to 13.4%. The case
where the lockless index calculation has to be redone is less than 0.01%.

With a real world test case (networking) we observed the following changes:

            Before        After
 Match:      97.8%        99.7%
 Requeue:     2.2%         0.3%
 Recalc:                  <0.001%

That means two percent fewer lock/requeue/unlock operations done in one of
the hot path use cases of timers.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.778527749@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:12 +02:00
Anna-Maria Gleixner
ffdf047728 timers: Split out index calculation
For further optimizations we need to seperate index calculation
from queueing. No functional change.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.691159619@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:12 +02:00
Thomas Gleixner
4e85876a9d timers: Only wake softirq if necessary
With the wheel forwading in place and with the HZ=1000 4ms folding we can
avoid running the softirq at all.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.607650550@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:11 +02:00
Thomas Gleixner
a683f390b9 timers: Forward the wheel clock whenever possible
The wheel clock is stale when a CPU goes into a long idle sleep. This has the
side effect that timers which are queued end up in the outer wheel levels.
That results in coarser granularity.

To solve this, we keep track of the idle state and forward the wheel clock
whenever possible.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.512039360@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:11 +02:00
Thomas Gleixner
ff00673292 timers/nohz: Remove pointless tick_nohz_kick_tick() function
This was a failed attempt to optimize the timer expiry in idle, which was
disabled and never revisited. Remove the cruft.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.431073782@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:10 +02:00
Anna-Maria Gleixner
236968383c timers: Optimize collect_expired_timers() for NOHZ
After a NOHZ idle sleep the timer wheel must be forwarded to current jiffies.
There might be expired timers so the current code loops and checks the expired
buckets for timers. This can take quite some time for long NOHZ idle periods.

The pending bitmask in the timer base allows us to do a quick search for the
next expiring timer and therefore a fast forward of the base time which
prevents pointless long lasting loops.

For a 3 seconds idle sleep this reduces the catchup time from ~1ms to 5us.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.351296290@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:10 +02:00
Anna-Maria Gleixner
73420fea80 timers: Move __run_timers() function
Move __run_timers() below __next_timer_interrupt() and next_pending_bucket()
in preparation for __run_timers() NOHZ optimization.

No functional change.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.271872665@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:09 +02:00
Thomas Gleixner
53bf837b78 timers: Remove set_timer_slack() leftovers
We now have implicit batching in the timer wheel. The slack API is no longer
used, so remove it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew F. Davis <afd@ti.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jaehoon Chung <jh80.chung@samsung.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Nyman <mathias.nyman@intel.com>
Cc: Pali Rohár <pali.rohar@gmail.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: linux-block@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mmc@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.189813118@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:09 +02:00
Thomas Gleixner
500462a9de timers: Switch to a non-cascading wheel
The current timer wheel has some drawbacks:

1) Cascading:

   Cascading can be an unbound operation and is completely pointless in most
   cases because the vast majority of the timer wheel timers are canceled or
   rearmed before expiration. (They are used as timeout safeguards, not as
   real timers to measure time.)

2) No fast lookup of the next expiring timer:

   In NOHZ scenarios the first timer soft interrupt after a long NOHZ period
   must fast forward the base time to the current value of jiffies. As we
   have no way to find the next expiring timer fast, the code loops linearly
   and increments the base time one by one and checks for expired timers
   in each step. This causes unbound overhead spikes exactly in the moment
   when we should wake up as fast as possible.

After a thorough analysis of real world data gathered on laptops,
workstations, webservers and other machines (thanks Chris!) I came to the
conclusion that the current 'classic' timer wheel implementation can be
modified to address the above issues.

The vast majority of timer wheel timers is canceled or rearmed before
expiry. Most of them are timeouts for networking and other I/O tasks. The
nature of timeouts is to catch the exception from normal operation (TCP ack
timed out, disk does not respond, etc.). For these kinds of timeouts the
accuracy of the timeout is not really a concern. Timeouts are very often
approximate worst-case values and in case the timeout fires, we already
waited for a long time and performance is down the drain already.

The few timers which actually expire can be split into two categories:

 1) Short expiry times which expect halfways accurate expiry

 2) Long term expiry times are inaccurate today already due to the
    batching which is done for NOHZ automatically and also via the
    set_timer_slack() API.

So for long term expiry timers we can avoid the cascading property and just
leave them in the less granular outer wheels until expiry or
cancelation. Timers which are armed with a timeout larger than the wheel
capacity are no longer cascaded. We expire them with the longest possible
timeout (6+ days). We have not observed such timeouts in our data collection,
but at least we handle them, applying the rule of the least surprise.

To avoid extending the wheel levels for HZ=1000 so we can accomodate the
longest observed timeouts (5 days in the network conntrack code) we reduce the
first level granularity on HZ=1000 to 4ms, which effectively is the same as
the HZ=250 behaviour. From our data analysis there is nothing which relies on
that 1ms granularity and as a side effect we get better batching and timer
locality for the networking code as well.

Contrary to the classic wheel the granularity of the next wheel is not the
capacity of the first wheel. The granularities of the wheels are in the
currently chosen setting 8 times the granularity of the previous wheel.

So for HZ=250 we end up with the following granularity levels:

 Level Offset   Granularity                  Range
     0      0          4 ms                 0 ms -        252 ms
     1     64         32 ms               256 ms -       2044 ms (256ms - ~2s)
     2    128        256 ms              2048 ms -      16380 ms (~2s   - ~16s)
     3    192       2048 ms (~2s)       16384 ms -     131068 ms (~16s  - ~2m)
     4    256      16384 ms (~16s)     131072 ms -    1048572 ms (~2m   - ~17m)
     5    320     131072 ms (~2m)     1048576 ms -    8388604 ms (~17m  - ~2h)
     6    384    1048576 ms (~17m)    8388608 ms -   67108863 ms (~2h   - ~18h)
     7    448    8388608 ms (~2h)    67108864 ms -  536870911 ms (~18h  - ~6d)

That's a worst case inaccuracy of 12.5% for the timers which are queued at the
beginning of a level.

So the new wheel concept addresses the old issues:

1) Cascading is avoided completely

2) By keeping the timers in the bucket until expiry/cancelation we can track
   the buckets which have timers enqueued in a bucket bitmap and therefore can
   look up the next expiring timer very fast and O(1).

A further benefit of the concept is that the slack calculation which is done
on every timer start is no longer necessary because the granularity levels
provide natural batching already.

Our extensive testing with various loads did not show any performance
degradation vs. the current wheel implementation.

This patch does not address the 'fast lookup' issue as we wanted to make sure
that there is no regression introduced by the wheel redesign. The
optimizations are in follow up patches.

This patch contains fixes from Anna-Maria Gleixner and Richard Cochran.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094342.108621834@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:09 +02:00
Thomas Gleixner
494af3ed78 timers: Give a few structs and members proper names
Some of the names in the internal implementation of the timer code
are not longer correct and others are simply too long to type.

Clean it up before we switch the wheel implementation over to
the new scheme.

No functional change.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.948752516@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:08 +02:00
Thomas Gleixner
177ec0a0a5 timers: Remove the deprecated mod_timer_pinned() API
We switched all users to initialize the timers as pinned and call
mod_timer(). Remove the now unused timer API function.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.706205231@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:35:06 +02:00
Thomas Gleixner
e675447bda timers: Make 'pinned' a timer property
We want to move the timer migration logic from a 'push' to a 'pull' model.

Under the current 'push' model pinned timers are handled via
a runtime API variant: mod_timer_pinned().

The 'pull' model requires us to store the pinned attribute of a timer
in the timer_list structure itself, as a new TIMER_PINNED bit in
timer->flags.

This flag must be set at initialization time and the timer APIs
recognize the flag.

This patch:

 - Implements the new flag and associated new-style initialization
   methods

 - makes mod_timer() recognize new-style pinned timers,

 - and adds some migration helper facility to allow
   step by step conversion of old-style to new-style
   pinned timers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Chris Mason <clm@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: George Spelvin <linux@sciencehorizons.net>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160704094341.049338558@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-07 10:25:13 +02:00
Jisheng Zhang
5130213721 tick/broadcast-hrtimer: Set name of the ce_broadcast_hrtimer
This is to avoid the "null" name when we either

~ # cat /sys/devices/system/clockevents/broadcast/current_device
(null)

or

~ # cat /proc/timer_list
...
Tick Device: mode:     1
Broadcast device
Clock Event Device: (null)
...

Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1467709071-3667-1-git-send-email-jszhang@marvell.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-07-05 17:02:19 +02:00
Ingo Molnar
0de7611a10 timers/nohz: Capitalize 'CPU' consistently
While reviewing another patch I noticed that kernel/time/tick-sched.c
had a charmingly (confusingly, annoyingly) rich set of variants for
spelling 'CPU':

  cpu
  cpus
  CPU
  CPUs
  per CPU
  per-CPU
  per cpu

... sometimes these were mixed even within the same comment block!

Compress these variants down to a single consistent set of:

  CPU
  CPUs
  per-CPU

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-01 12:45:34 +02:00
Wei Jiangang
6168f8ed01 timers/nohz: Fix several typos
Signed-off-by: Wei Jiangang <weijg.fnst@cn.fujitsu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: fenghua.yu@intel.com
Link: http://lkml.kernel.org/r/1467175910-2966-2-git-send-email-weijg.fnst@cn.fujitsu.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2016-07-01 12:39:22 +02:00
Gregor Boirie
eaaa7ec71b timekeeping: export get_monotonic_coarse64 symbol
EXPORT_SYMBOL() get_monotonic_coarse64 for new IIO timestamping clock
selection usage. This provides user apps the ability to request a
particular IIO device to timestamp samples using a monotonic coarse clock
granularity.

Signed-off-by: Gregor Boirie <gregor.boirie@parrot.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
2016-06-30 19:41:23 +01:00
Thomas Gleixner
c7d6b5a22c Merge branch 'fortglx/4.8/time' of https://git.linaro.org/people/john.stultz/linux into timers/core
Pull time(keeping) updates from John Stultz:

 - Handle the 1ns issue with the old refusing to die vsyscall machinery
 - More y2038 updates
 - Documentation fixes
 - Simplify clocksource handling
2016-06-21 08:22:51 +02:00
Arnd Bergmann
7c71feb0a6 timer: Avoid using timespec
The tstats_show() function prints a ktime_t variable by converting
it to struct timespec first. The algorithm is ok, but we want to
stop using timespec in general because of the 32-bit time_t
overflow problem.

This changes the code to use struct timespec64, without any
functional change.

Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-06-20 12:47:33 -07:00
Arnd Bergmann
4a19bd3d22 time: Avoid timespec in udelay_test
udelay_test_single() uses ktime_get_ts() to get two timespec values
and calculate the difference between them, while udelay_test_show()
uses the same to printk() the current monotonic time.

Both of these are y2038 safe on all machines, but we want to
get rid of struct timespec anyway, so this converts the code to
use ktime_get_ns() and ktime_get_ts64() respectively.

Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-06-20 12:47:26 -07:00
Deepa Dinamani
e6c2682a1d time: Add time64_to_tm()
time_to_tm() takes time_t as an argument.
time_t is not y2038 safe.
Add time64_to_tm() that takes time64_t as an argument
which is y2038 safe.
The plan is to eventually replace all calls to time_to_tm()
by time64_to_tm().

Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-06-20 12:47:15 -07:00
Pratyush Patel
af4afb4008 alarmtimer: Fix comments describing structure fields
Updated struct alarm and struct alarm_timer descriptions.

Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Pratyush Patel <pratyushpatel.1995@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-06-20 12:47:09 -07:00
Thomas Graziadei
0209b93756 timekeeping: Fix 1ns/tick drift with GENERIC_TIME_VSYSCALL_OLD
The user notices the problem in a raw and real time drift, calling
clock_gettime with CLOCK_REALTIME / CLOCK_MONOTONIC_RAW on a system
with no ntp correction taking place (no ntpd or ptp stuff running).

The problem is, that old_vsyscall_fixup adds an extra 1ns even though
xtime_nsec is already held in full nsecs and the remainder in this
case is 0. Do the rounding up buisness only if needed.

Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Thomas Graziadei <thomas.graziadei@omicronenergy.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-06-20 12:46:45 -07:00
Minfei Huang
0fb71d340d clocksource: Make clocksource insert entry more efficient
In clocksource_enqueue(), it is unnecessary to continue looping
the list, if we find there is an entry that the value of rating
is smaller than the new one. It is safe to be out the loop,
because all of entry are inserted in descending order.

Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Minfei Huang <mnghuan@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
2016-06-20 12:46:34 -07:00
Pratyush Patel
86721ab63b hrtimer: Remove redundant #ifdef block
Only need CONFIG_NO_HZ_COMMON as this block is already in a
CONFIG_SMP block.

Signed-off-by: Pratyush Patel <pratyushpatel.1995@gmail.com>
Link: http://lkml.kernel.org/r/20160301172849.GA18152@cyborg
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-06-10 11:25:35 +02:00
Bjorn Helgaas
b5227d03b7 timers: Clarify usleep_range() function comment
Update the usleep_range() function comment to make it clear that it can
only be used in non-atomic context.

Previously we claimed usleep_range() was a drop-in replacement for udelay()
where wakeup is flexible.  But that's only true in non-atomic contexts,
where it's possible to sleep instead of delay.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20160531212302.28502.44995.stgit@bhelgaas-glaptop2.roam.corp.google.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-06-10 00:59:14 +02:00
Guenter Roeck
c08376ac97 timer: Export destroy_hrtimer_on_stack()
hrtimer_init_on_stack() needs a matching call to
destroy_hrtimer_on_stack(), so both need to be exported.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-05-31 11:44:08 -07:00
Du, Changbin
b9fdac7f66 debugobjects: insulate non-fixup logic related to static obj from fixup callbacks
When activating a static object we need make sure that the object is
tracked in the object tracker.  If it is a non-static object then the
activation is illegal.

In previous implementation, each subsystem need take care of this in
their fixup callbacks.  Actually we can put it into debugobjects core.
Thus we can save duplicated code, and have *pure* fixup callbacks.

To achieve this, a new callback "is_static_object" is introduced to let
the type specific code decide whether a object is static or not.  If
yes, we take it into object tracker, otherwise give warning and invoke
fixup callback.

This change has paassed debugobjects selftest, and I also do some test
with all debugobjects supports enabled.

At last, I have a concern about the fixups that can it change the object
which is in incorrect state on fixup? Because the 'addr' may not point
to any valid object if a non-static object is not tracked.  Then Change
such object can overwrite someone's memory and cause unexpected
behaviour.  For example, the timer_fixup_activate bind timer to function
stub_timer.

Link: http://lkml.kernel.org/r/1462576157-14539-1-git-send-email-changbin.du@intel.com
[changbin.du@intel.com: improve code comments where invoke the new is_static_object callback]
  Link: http://lkml.kernel.org/r/1462777431-8171-1-git-send-email-changbin.du@intel.com
Signed-off-by: Du, Changbin <changbin.du@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Triplett <josh@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-19 19:12:14 -07:00
Du, Changbin
e3252464da timer: update debugobjects fixup callbacks return type
Update the return type to use bool instead of int, corresponding to
cheange (debugobjects: make fixup functions return bool instead of int).

Signed-off-by: Du, Changbin <changbin.du@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Josh Triplett <josh@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-19 19:12:14 -07:00
Deepa Dinamani
8e4f70e218 time: remove timespec_add_safe()
All references to timespec_add_safe() now use timespec64_add_safe().

The plan is to replace struct timespec references with struct timespec64
throughout the kernel as timespec is not y2038 safe.

Drop timespec_add_safe() and use timespec64_add_safe() for all
architectures.

Link: http://lkml.kernel.org/r/1461947989-21926-4-git-send-email-deepa.kernel@gmail.com
Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-19 19:12:14 -07:00