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Commit 6a24474d authored by Tejun Heo's avatar Tejun Heo
Browse files

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



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: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Acked-by: default avatarKent Overstreet <koverstreet@google.com>
parent c1ae6e9b

include/linux/percpu-refcount.h

+4 −4
Original line number Original line Diff line number Diff line
@@ -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