Commit e3d85487 authored Jul 10, 2019 by Peter Zijlstra Committed by Ingo Molnar Jul 13, 2019

sched/core: Fix preempt warning in ttwu



John reported a DEBUG_PREEMPT warning caused by commit:

  aacedf26 ("sched/core: Optimize try_to_wake_up() for local wakeups")

I overlooked that ttwu_stat() requires preemption disabled.

Reported-by: John Stultz <john.stultz@linaro.org>
Tested-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: aacedf26 ("sched/core: Optimize try_to_wake_up() for local wakeups")
Link: https://lkml.kernel.org/r/20190710105736.GK3402@hirez.programming.kicks-ass.net


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent f632a817

kernel/sched/core.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -2399,6 +2399,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
		unsigned long flags;
		int cpu, success = 0;

		preempt_disable();
		if (p == current) {
		/*
		* We're waking current, this means 'p->on_rq' and 'task_cpu(p)
		@@ -2412,7 +2413,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
		* it disabling IRQs (this allows not taking ->pi_lock).
		*/
		if (!(p->state & state))
		return false;
		goto out;

		success = 1;
		cpu = task_cpu(p);
		@@ -2526,6 +2527,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
		out:
		if (success)
		ttwu_stat(p, cpu, wake_flags);
		preempt_enable();

		return success;
		}