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sched: Add missing rcu protection to wake_up_all_idle_cpus

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Locklessly doing is_idle_task(rq->curr) is only okay because of
RCU protection.  The older variant of the broken code checked
rq->curr == rq->idle instead and therefore didn't need RCU.

Fixes: f6be8af1c9 ("sched: Add new API wake_up_if_idle() to wake up the idle cpu")
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: Chuansheng Liu <chuansheng.liu@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/729365dddca178506dfd0a9451006344cd6808bc.1417277372.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2014-11-29 08:13:51 -08:00 committed by Ingo Molnar
parent 36ce98818a
commit fd7de1e8d5
1 changed files with 7 additions and 2 deletions
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9
kernel/sched/core.c
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@ -1628,8 +1628,10 @@ void wake_up_if_idle(int cpu)
struct rq *rq = cpu_rq(cpu); struct rq *rq = cpu_rq(cpu);
unsigned long flags; unsigned long flags;
if (!is_idle_task(rq->curr)) rcu_read_lock();
return;
if (!is_idle_task(rcu_dereference(rq->curr)))
goto out;
if (set_nr_if_polling(rq->idle)) { if (set_nr_if_polling(rq->idle)) {
trace_sched_wake_idle_without_ipi(cpu); trace_sched_wake_idle_without_ipi(cpu);
@ -1640,6 +1642,9 @@ void wake_up_if_idle(int cpu)
/* Else cpu is not in idle, do nothing here */ /* Else cpu is not in idle, do nothing here */
raw_spin_unlock_irqrestore(&rq->lock, flags); raw_spin_unlock_irqrestore(&rq->lock, flags);
} }
out:
rcu_read_unlock();
} }
bool cpus_share_cache(int this_cpu, int that_cpu) bool cpus_share_cache(int this_cpu, int that_cpu)