linux-kernel - [PATCH 09/16] percpu: Replace smp_read_barrier_depends() with lockless

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Date:	Thu, 13 Nov 2014 14:24:15 -0500
From:	Pranith Kumar <bobby.prani@...il.com>
To:	Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	linux-kernel@...r.kernel.org (open list)
Cc:	paulmck@...ux.vnet.ibm.com
Subject: [PATCH 09/16] percpu: Replace smp_read_barrier_depends() with lockless_dereference()

Recently lockless_dereference() was added which can be used in place of
hard-coding smp_read_barrier_depends(). The following PATCH makes the change.

Signed-off-by: Pranith Kumar <bobby.prani@...il.com>
---
 include/linux/percpu-refcount.h | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h
index 494ab05..3cf6759 100644
--- a/include/linux/percpu-refcount.h
+++ b/include/linux/percpu-refcount.h
@@ -128,10 +128,8 @@ static inline void percpu_ref_kill(struct percpu_ref *ref)
 static inline bool __ref_is_percpu(struct percpu_ref *ref,
 					  unsigned long __percpu **percpu_countp)
 {
-	unsigned long percpu_ptr = ACCESS_ONCE(ref->percpu_count_ptr);
-
 	/* paired with smp_store_release() in percpu_ref_reinit() */
-	smp_read_barrier_depends();
+	unsigned long percpu_ptr = lockless_dereference(ref->percpu_count_ptr);
 
 	if (unlikely(percpu_ptr & __PERCPU_REF_ATOMIC))
 		return false;
-- 
1.9.1

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