From: Valentin Schneider <[email protected]> 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.
cc: Ingo Molnar <[email protected]> cc: Peter Zijlstra <[email protected]> Signed-off-by: Valentin Schneider <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> --- kernel/sched/fair.c | 6 +++--- kernel/sched/sched.h | 4 ++-- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 545fa3600894..9dd147c71dd0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8431,8 +8431,8 @@ 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); } } @@ -9875,7 +9875,7 @@ 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); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index f945edadd2c5..791d9badad31 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1665,8 +1665,8 @@ 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 } -- 2.7.4
