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percpu-refcount: consistently use plain (non-sched) RCU

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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 <tj@kernel.org>
Reported-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Kent Overstreet <koverstreet@google.com>
This commit is contained in:
Tejun Heo 2013-06-12 20:43:06 -07:00
parent c1ae6e9b4d
commit 6a24474da8
1 changed files with 4 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
include/linux/percpu-refcount.h
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@ -85,7 +85,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
{ {
unsigned __percpu *pcpu_count; unsigned __percpu *pcpu_count;
preempt_disable(); rcu_read_lock();
pcpu_count = ACCESS_ONCE(ref->pcpu_count); pcpu_count = ACCESS_ONCE(ref->pcpu_count);
@ -94,7 +94,7 @@ static inline void percpu_ref_get(struct percpu_ref *ref)
else else
atomic_inc(&ref->count); 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; unsigned __percpu *pcpu_count;
preempt_disable(); rcu_read_lock();
pcpu_count = ACCESS_ONCE(ref->pcpu_count); 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))) else if (unlikely(atomic_dec_and_test(&ref->count)))
ref->release(ref); ref->release(ref);
preempt_enable(); rcu_read_unlock();
} }
#endif #endif