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Commit acac7883 authored by Tejun Heo's avatar Tejun Heo
Browse files

percpu-refcount: add __must_check to percpu_ref_init() and don't use... 


percpu-refcount: add __must_check to percpu_ref_init() and don't use ACCESS_ONCE() in percpu_ref_kill_rcu()

Two small changes.

* Unlike most init functions, percpu_ref_init() allocates memory and
  may fail.  Let's mark it with __must_check in case the caller
  forgets.

* percpu_ref_kill_rcu() is unnecessarily using ACCESS_ONCE() to
  dereference @ref->pcpu_count, which can be misleading.  The pointer
  is guaranteed to be valid and visible and can't change underneath
  the function.  Drop ACCESS_ONCE().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent ac899061

include/linux/percpu-refcount.h

+2 −1
Original line number Diff line number Diff line
@@ -66,7 +66,8 @@ struct percpu_ref { 
	struct rcu_head		rcu;

};



int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release);

int __must_check percpu_ref_init(struct percpu_ref *ref,

				 percpu_ref_func_t *release);

void percpu_ref_kill(struct percpu_ref *ref);



#define PCPU_STATUS_BITS	2

lib/percpu-refcount.c

+1 −3
Original line number Diff line number Diff line
@@ -57,12 +57,10 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release) 
static void percpu_ref_kill_rcu(struct rcu_head *rcu)

{

	struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu);

	unsigned __percpu *pcpu_count;

	unsigned __percpu *pcpu_count = ref->pcpu_count;

	unsigned count = 0;

	int cpu;



	pcpu_count = ACCESS_ONCE(ref->pcpu_count);



	/* Mask out PCPU_REF_DEAD */

	pcpu_count = (unsigned __percpu *)

		(((unsigned long) pcpu_count) & ~PCPU_STATUS_MASK);