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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: 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>
This commit is contained in:
Valentin Schneider 2018-07-04 11:17:46 +01:00 committed by Ingo Molnar
parent 575638d104
commit e90c8fe15a
2 changed files with 5 additions and 5 deletions
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6
kernel/sched/fair.c
View File

@ -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);

4
kernel/sched/sched.h
View File

@ -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
}