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sched/clock: Fix clear_sched_clock_stable() preempt wobbly 

Paul reported a problems with clear_sched_clock_stable(). Since we run
all of __clear_sched_clock_stable() from workqueue context, there's a
preempt problem.

Solve it by only running the static_key_disable() from workqueue.

Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: fweisbec@gmail.com
Link: http://lkml.kernel.org/r/20170313124621.GA3328@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
hifive-unleashed-5.1
Peter Zijlstra 2017-03-13 13:46:21 +01:00 committed by Ingo Molnar
parent 093b995e3b
commit 71fdb70eb4
1 changed files with 12 additions and 5 deletions
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17
kernel/sched/clock.c
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@ -141,7 +141,14 @@ static void __set_sched_clock_stable(void)
tick_dep_clear(TICK_DEP_BIT_CLOCK_UNSTABLE);
}
static void __clear_sched_clock_stable(struct work_struct *work)
static void __sched_clock_work(struct work_struct *work)
{
static_branch_disable(&__sched_clock_stable);
}
static DECLARE_WORK(sched_clock_work, __sched_clock_work);
static void __clear_sched_clock_stable(void)
{
struct sched_clock_data *scd = this_scd();
@ -160,11 +167,11 @@ static void __clear_sched_clock_stable(struct work_struct *work)
scd->tick_gtod, gtod_offset,
scd->tick_raw, raw_offset);
static_branch_disable(&__sched_clock_stable);
tick_dep_set(TICK_DEP_BIT_CLOCK_UNSTABLE);
}
static DECLARE_WORK(sched_clock_work, __clear_sched_clock_stable);
if (sched_clock_stable())
schedule_work(&sched_clock_work);
}
void clear_sched_clock_stable(void)
{
@ -173,7 +180,7 @@ void clear_sched_clock_stable(void)
smp_mb(); /* matches sched_clock_init_late() */
if (sched_clock_running == 2)
schedule_work(&sched_clock_work);
__clear_sched_clock_stable();
}
void sched_clock_init_late(void)