Messages in this thread Patch in this message | | | Subject | Re: [BUG -tip/sched] INFO: suspicious RCU usage | From | Peter Zijlstra <> | Date | Wed, 07 Dec 2011 14:32:08 +0100 |
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I made that
--- Subject: sched, nohz: Fix missing RCU read lock From: Peter Zijlstra <a.p.zijlstra@chello.nl> Date: Wed Dec 07 14:28:44 CET 2011
Yong Zhang reported:
> [ INFO: suspicious RCU usage. ] > kernel/sched/fair.c:5091 suspicious rcu_dereference_check() usage!
This is due to the sched_domain stuff being RCU protected and commit 0b005cf5 ("sched, nohz: Implement sched group, domain aware nohz idle load balancing") overlooking this fact.
The sd variable only lives inside the for_each_domain() block, so we only need to wrap that.
Cc: Suresh Siddha <suresh.b.siddha@intel.com> Reported-by: Yong Zhang <yong.zhang0@gmail.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/n/tip-gt616u9aetdzgb1oc4m6uydr@git.kernel.org --- Index: linux-2.6/kernel/sched/fair.c =================================================================== --- linux-2.6.orig/kernel/sched/fair.c +++ linux-2.6/kernel/sched/fair.c @@ -5088,23 +5088,28 @@ static inline int nohz_kick_needed(struc if (rq->nr_running >= 2) goto need_kick; + rcu_read_lock(); for_each_domain(cpu, sd) { struct sched_group *sg = sd->groups; struct sched_group_power *sgp = sg->sgp; int nr_busy = atomic_read(&sgp->nr_busy_cpus); if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1) - goto need_kick; + goto need_kick_unlock; if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight && (cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu)) - goto need_kick; + goto need_kick_unlock; if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING))) break; } + rcu_read_unlock(); return 0; + +need_kick_unlock: + rcu_read_unlock(); need_kick: return 1; }
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