Commit-ID: fd7de1e8d5b2b2b35e71332fafb899f584597150
Gitweb: http://git.kernel.org/tip/fd7de1e8d5b2b2b35e71332fafb899f584597150
Author: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
AuthorDate: Sat, 29 Nov 2014 08:13:51 -0800
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 8 Dec 2014 11:44:19 +0100
sched: Add missing rcu protection to wake_up_all_idle_cpus
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@xxxxxxxxxxxxxx>
Reviewed-by: Chuansheng Liu <chuansheng.liu@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/729365dddca178506dfd0a9451006344cd6808bc.1417277372.git.luto@xxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/core.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d44d0c5..88f49bc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1628,8 +1628,10 @@ 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);
@@ -1640,6 +1642,9 @@ 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)
--
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