linux-kernel - [PATCH] kernel/events/core.c: Replace rcu_dereference() with rcu_access

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Date:	Sun, 17 Aug 2014 15:34:31 +0300
From:	Andreea-Cristina Bernat <bernat.ada@...il.com>
To:	a.p.zijlstra@...llo.nl, paulus@...ba.org, mingo@...hat.com,
	acme@...nel.org, linux-kernel@...r.kernel.org
Cc:	paulmck@...ux.vnet.ibm.com
Subject: [PATCH] kernel/events/core.c: Replace rcu_dereference() with
 rcu_access_pointer()

The "rcu_dereference()" call is used directly in a condition.
Since its return value is never dereferenced it is recommended to use
"rcu_access_pointer()" instead of "rcu_dereference()".
Therefore, this patch makes the replacement.

The following Coccinelle semantic patch was used:
@@
@@

(
 if(
 (<+...
- rcu_dereference
+ rcu_access_pointer
  (...)
  ...+>)) {...}
|
 while(
 (<+...
- rcu_dereference
+ rcu_access_pointer
  (...)
  ...+>)) {...}
)

Signed-off-by: Andreea-Cristina Bernat <bernat.ada@...il.com>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 5fa58e4..0d735be 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -980,7 +980,7 @@ retry:
 		 * can't get swapped on us any more.
 		 */
 		raw_spin_lock_irqsave(&ctx->lock, *flags);
-		if (ctx != rcu_dereference(task->perf_event_ctxp[ctxn])) {
+		if (ctx != rcu_access_pointer(task->perf_event_ctxp[ctxn])) {
 			raw_spin_unlock_irqrestore(&ctx->lock, *flags);
 			rcu_read_unlock();
 			preempt_enable();
-- 
1.9.1

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