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Commit 6497830f authored by Valentin Schneider's avatar Valentin Schneider Committed by Quentin Perret
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UPSTREAM: sched/fair: Wrap rq->rd->overload accesses with READ/WRITE_ONCE() 



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: default avatarValentin Schneider <valentin.schneider@arm.com>
Signed-off-by: default avatarMorten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
(cherry picked from commit e90c8fe15a3bf93a23088bcf1a56a0fa391d4e50)
Signed-off-by: default avatarQuentin Perret <quentin.perret@arm.com>

Change-Id: Id46db398099d15a051566806f7ca0092d3973788
parent f68d8feb

kernel/sched/fair.c

+3 −3
Original line number Diff line number Diff line
@@ -8152,8 +8152,8 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd 


	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);

	}

}
@@ -9596,7 +9596,7 @@ 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
@@ -1700,8 +1700,8 @@ 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

	}