linux_dsm_epyc7002/kernel/time
Peter Zijlstra 5de2755c8c hrtimer: Allow concurrent hrtimer_start() for self restarting timers
Because we drop cpu_base->lock around calling hrtimer::function, it is
possible for hrtimer_start() to come in between and enqueue the timer.

If hrtimer::function then returns HRTIMER_RESTART we'll hit the BUG_ON
because HRTIMER_STATE_ENQUEUED will be set.

Since the above is a perfectly valid scenario, remove the BUG_ON and
make the enqueue_hrtimer() call conditional on the timer not being
enqueued already.

NOTE: in that concurrent scenario its entirely common for both sites
to want to modify the hrtimer, since hrtimers don't provide
serialization themselves be sure to provide some such that the
hrtimer::function and the hrtimer_start() caller don't both try and
fudge the expiration state at the same time.

To that effect, add a WARN when someone tries to forward an already
enqueued timer, the most common way to change the expiry of self
restarting timers. Ideally we'd put the WARN in everything modifying
the expiry but most of that is inlines and we don't need the bloat.

Fixes: 2d44ae4d71 ("hrtimer: clean up cpu->base locking tricks")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20150415113105.GT5029@twins.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2015-04-22 17:06:52 +02:00
..
alarmtimer.c alarmtimer: Get rid of unused return value 2015-04-22 17:06:52 +02:00
clockevents.c clockevents: Cleanup dead cpu explicitely 2015-04-03 08:44:37 +02:00
clocksource.c clocksource: Improve comment explaining clocks_calc_max_nsecs()'s 50% safety margin 2015-04-03 08:18:35 +02:00
hrtimer.c hrtimer: Allow concurrent hrtimer_start() for self restarting timers 2015-04-22 17:06:52 +02:00
itimer.c time/timers: Move all time(r) related files into kernel/time 2014-06-23 11:22:35 +02:00
jiffies.c tick: Move clocksource related stuff to timekeeping.h 2015-04-01 14:22:58 +02:00
Kconfig clockevents: Remove CONFIG_GENERIC_CLOCKEVENTS_BUILD 2015-04-01 14:22:57 +02:00
Makefile clockevents: Remove CONFIG_GENERIC_CLOCKEVENTS_BUILD 2015-04-01 14:22:57 +02:00
ntp_internal.h timekeeping: Convert timekeeping core to use timespec64s 2014-07-23 10:17:54 -07:00
ntp.c time: Add y2038 safe update_persistent_clock64() 2015-04-03 08:18:20 +02:00
posix-clock.c
posix-cpu-timers.c all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
posix-timers.c hrtimer: Get rid of hrtimer_get_res() 2015-04-22 17:06:49 +02:00
sched_clock.c timers, sched/clock: Clean up the code a bit 2015-03-27 08:34:01 +01:00
test_udelay.c time: Rename udelay_test.c to test_udelay.c 2014-11-21 11:59:55 -08:00
tick-broadcast-hrtimer.c tick: broadcast-hrtimer: Remove overly clever return value abuse 2015-04-22 17:06:52 +02:00
tick-broadcast.c clockevents: Cleanup dead cpu explicitely 2015-04-03 08:44:37 +02:00
tick-common.c hrtimer: Get rid of hrtimer softirq 2015-04-22 17:06:50 +02:00
tick-internal.h tick: Nohz: Rework next timer evaluation 2015-04-22 17:06:50 +02:00
tick-oneshot.c clockevents: Manage device's state separately for the core 2015-03-27 10:26:19 +01:00
tick-sched.c tick: Nohz: Rework next timer evaluation 2015-04-22 17:06:50 +02:00
tick-sched.h tick: Nohz: Rework next timer evaluation 2015-04-22 17:06:50 +02:00
time.c Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-01-25 17:47:34 -08:00
timeconst.bc time/timers: Move all time(r) related files into kernel/time 2014-06-23 11:22:35 +02:00
timeconv.c
timecounter.c timecounter: keep track of accumulated fractional nanoseconds 2014-12-30 18:29:27 -05:00
timekeeping_debug.c timekeeping: Convert timekeeping core to use timespec64s 2014-07-23 10:17:54 -07:00
timekeeping_internal.h clocksource: Move cycle_last validation to core code 2014-07-23 15:01:51 -07:00
timekeeping.c hrtimer: Make offset update smarter 2015-04-22 17:06:49 +02:00
timekeeping.h hrtimer: Make offset update smarter 2015-04-22 17:06:49 +02:00
timer_list.c tick: Nohz: Rework next timer evaluation 2015-04-22 17:06:50 +02:00
timer_stats.c timer stats: Add a 'Collection: active/inactive' line to timer usage statistics 2013-10-10 09:59:25 +02:00
timer.c timer: Put usleep_range into the __sched section 2015-04-22 17:06:52 +02:00