From: Josh Triplett <josh@joshtriplett.org>
Date: Sun, 1 Sep 2013 23:42:52 +0000 (-0700)
Subject: rcu: Make rcu_assign_pointer's assignment volatile and type-safe
X-Git-Tag: v3.14-rc1~174^2^2^4~1
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=9d162cd06349dfee6b4f254b3abf1355cf0aee43;p=linux.git

rcu: Make rcu_assign_pointer's assignment volatile and type-safe

The rcu_assign_pointer() primitive needs to use ACCESS_ONCE to make
the assignment to the destination pointer volatile, to protect against
compilers too clever for their own good.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 00ad28168ef0..97853cd2d7b4 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -551,7 +551,7 @@ static inline void rcu_preempt_sleep_check(void)
 #define __rcu_assign_pointer(p, v, space) \
 	do { \
 		smp_wmb(); \
-		(p) = (typeof(*v) __force space *)(v); \
+		ACCESS_ONCE(p) = (typeof(*(v)) __force space *)(v); \
 	} while (0)