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| author | Andy Lutomirski <luto@amacapital.net> | 2014-11-29 08:13:51 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-01-16 06:59:54 -0800 |
| commit | 170f69f4cf0ef0431d52288644108fe09f68e3b8 (patch) | |
| tree | 6bd2467f6b0797151f8bfad475c6c8b74e620112 | |
| parent | f88708af7a43f1765b520f0fd9d8717ce77417e3 (diff) | |
| download | lwn-170f69f4cf0ef0431d52288644108fe09f68e3b8.tar.gz lwn-170f69f4cf0ef0431d52288644108fe09f68e3b8.zip | |
sched: Add missing rcu protection to wake_up_all_idle_cpus
commit fd7de1e8d5b2b2b35e71332fafb899f584597150 upstream.
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: f6be8af1c95d ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/sched/core.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 89e7283015a6..efdca2f08222 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1623,8 +1623,10 @@ void wake_up_if_idle(int cpu) struct rq *rq = cpu_rq(cpu); unsigned long flags; - if (!is_idle_task(rq->curr)) - return; + rcu_read_lock(); + + if (!is_idle_task(rcu_dereference(rq->curr))) + goto out; if (set_nr_if_polling(rq->idle)) { trace_sched_wake_idle_without_ipi(cpu); @@ -1635,6 +1637,9 @@ void wake_up_if_idle(int cpu) /* Else cpu is not in idle, do nothing here */ raw_spin_unlock_irqrestore(&rq->lock, flags); } + +out: + rcu_read_unlock(); } bool cpus_share_cache(int this_cpu, int that_cpu) |