linux-kernel - [RFC][PATCH] rcu: Use WRITE_ONCE in RCU_INIT

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Message-ID: <20150602152648.GT3644@twins.programming.kicks-ass.net>
Date:	Tue, 2 Jun 2015 17:26:48 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc:	josh@...htriplett.org, rostedt@...dmis.org,
	mathieu.desnoyers@...icios.com, laijs@...fujitsu.com,
	linux-kernel@...r.kernel.org
Subject: [RFC][PATCH] rcu: Use WRITE_ONCE in RCU_INIT_POINTER


For the paranoid amongst us GCC would be in its right to use byte stores
to write our NULL value, tell it not to do that.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 include/linux/rcupdate.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 33a056bb886f..e173847b6543 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -1046,7 +1046,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 #define RCU_INIT_POINTER(p, v) \
 	do { \
 		rcu_dereference_sparse(p, __rcu); \
-		p = RCU_INITIALIZER(v); \
+		WRITE_ONCE(p, RCU_INITIALIZER(v)); \
 	} while (0)
 
 /**
--
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