From: Tejun Heo <t...@kernel.org>
percpu_ref_get/put() are using preempt_disable/enable() while
percpu_ref_kill() is using plain call_rcu() instead of
call_rcu_sched(). This is buggy as grace periods of the two may not
match. Fix it by using plain RCU in percpu_ref_get/put().
(I suggested using sched RCU in the first place but there's no actual
benefit in doing so unless we're gonna introduce different variants
of get/put to be called while preemption is alredy disabled, which we
definitely shouldn't.)
Signed-off-by: Tejun Heo <t...@kernel.org>
Reported-by: Rusty Russell <ru...@rustcorp.com.au>
Acked-by: Kent Overstreet <koverstr...@google.com>
(cherry picked from commit 6a24474da83ea7c8b7d32f05f858b1259994067a)
Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
---
include/linux/percpu-refcount.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 24b31ef15932..abe141172d96 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -85,7 +85,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
{
unsigned __percpu *pcpu_count;
- preempt_disable();
+ rcu_read_lock();
pcpu_count = ACCESS_ONCE(ref->pcpu_count);
@@ -94,7 +94,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
else
atomic_inc(&ref->count);
- preempt_enable();
+ rcu_read_unlock();
}
/**
@@ -107,7 +107,7 @@ static inline void percpu_ref_put(struct percpu_ref *ref)
{
unsigned __percpu *pcpu_count;
- preempt_disable();
+ rcu_read_lock();
pcpu_count = ACCESS_ONCE(ref->pcpu_count);
@@ -116,7 +116,7 @@ static inline void percpu_ref_put(struct percpu_ref *ref)
else if (unlikely(atomic_dec_and_test(&ref->count)))
ref->release(ref);
- preempt_enable();
+ rcu_read_unlock();
}
#endif
--
2.1.4
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