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Commit c1ae6e9b authored by Kent Overstreet's avatar Kent Overstreet Committed by Tejun Heo
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percpu-refcount: Don't use silly cmpxchg() 



The cmpxchg() was just to ensure the debug check didn't race, which was
a bit excessive. The caller is supposed to do the appropriate
synchronization, which means percpu_ref_kill() can just do a simple
store.

Signed-off-by: default avatarKent Overstreet <koverstreet@google.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 215e262f

lib/percpu-refcount.c

+4 −15
Original line number Diff line number Diff line
@@ -107,22 +107,11 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) 
 */

void percpu_ref_kill(struct percpu_ref *ref)

{

	unsigned __percpu *pcpu_count, *old, *new;

	WARN_ONCE(REF_STATUS(ref->pcpu_count) == PCPU_REF_DEAD,

		  "percpu_ref_kill() called more than once!\n");



	pcpu_count = ACCESS_ONCE(ref->pcpu_count);



	do {

		if (REF_STATUS(pcpu_count) == PCPU_REF_DEAD) {

			WARN(1, "percpu_ref_kill() called more than once!\n");

			return;

		}



		old = pcpu_count;

		new = (unsigned __percpu *)

			(((unsigned long) pcpu_count)|PCPU_REF_DEAD);



		pcpu_count = cmpxchg(&ref->pcpu_count, old, new);

	} while (pcpu_count != old);

	ref->pcpu_count = (unsigned __percpu *)

		(((unsigned long) ref->pcpu_count)|PCPU_REF_DEAD);



	call_rcu(&ref->rcu, percpu_ref_kill_rcu);

}