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Commit 71fdb70e authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 093b995e

kernel/sched/clock.c

+12 −5
Original line number Diff line number Diff line
@@ -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)