sched/fair: Wrap rq->rd->overload accesses with READ/WRITE_ONCE() (e90c8fe1) · Commits · 戴 / test

This variable can be read and set locklessly within update_sd_lb_stats(). As such, READ/WRITE_ONCE() are added to make sure nothing terribly wrong can happen because of the compiler. Signed-off-by:

Valentin Schneider <valentin.schneider@arm.com> Signed-off-by:

Morten Rasmussen <morten.rasmussen@arm.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: dietmar.eggemann@arm.com Cc: gaku.inami.xh@renesas.com Cc: vincent.guittot@linaro.org Link: http://lkml.kernel.org/r/1530699470-29808-9-git-send-email-morten.rasmussen@arm.com Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/sched/fair.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -8058,8 +8058,8 @@ next_group:

		if (!env->sd->parent) {
		/* update overload indicator if we are at root domain */
		if (env->dst_rq->rd->overload != overload)
		env->dst_rq->rd->overload = overload;
		if (READ_ONCE(env->dst_rq->rd->overload) != overload)
		WRITE_ONCE(env->dst_rq->rd->overload, overload);
		}
		}

		@@ -9502,7 +9502,7 @@ static int idle_balance(struct rq this_rq, struct rq_flags rf)
		rq_unpin_lock(this_rq, rf);

		if (this_rq->avg_idle < sysctl_sched_migration_cost \|\|
		!this_rq->rd->overload) {
		!READ_ONCE(this_rq->rd->overload)) {

		rcu_read_lock();
		sd = rcu_dereference_check_sched_domain(this_rq->sd);

kernel/sched/sched.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -1697,8 +1697,8 @@ static inline void add_nr_running(struct rq *rq, unsigned count)

		if (prev_nr < 2 && rq->nr_running >= 2) {
		#ifdef CONFIG_SMP
		if (!rq->rd->overload)
		rq->rd->overload = 1;
		if (!READ_ONCE(rq->rd->overload))
		WRITE_ONCE(rq->rd->overload, 1);
		#endif
		}

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