This is a note to let you know that I've just added the patch titled
sched: Add missing rcu protection to wake_up_all_idle_cpus
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-add-missing-rcu-protection-to-wake_up_all_idle_cpus.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From fd7de1e8d5b2b2b35e71332fafb899f584597150 Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <[email protected]>
Date: Sat, 29 Nov 2014 08:13:51 -0800
Subject: sched: Add missing rcu protection to wake_up_all_idle_cpus
From: Andy Lutomirski <[email protected]>
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 <[email protected]>
Reviewed-by: Chuansheng Liu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link:
http://lkml.kernel.org/r/729365dddca178506dfd0a9451006344cd6808bc.1417277372.git.l...@amacapital.net
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/sched/core.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
--- 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)
Patches currently in stable-queue which might be from [email protected] are
queue-3.18/sched-add-missing-rcu-protection-to-wake_up_all_idle_cpus.patch
queue-3.18/x86-vdso-use-asm-volatile-in-__getcpu.patch
queue-3.18/x86_64-vdso-fix-the-vdso-address-randomization-algorithm.patch
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