From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Fri, 9 Aug 2013 05:26:23 +0000 (-0700)
Subject: rcu: Flag lockless access to ->gp_flags with ACCESS_ONCE()
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=591c6d1710cd73824057d08eda302cf2a7cfd18a;p=linux-beck.git

rcu: Flag lockless access to ->gp_flags with ACCESS_ONCE()

This commit applies ACCESS_ONCE() to an outside-of-lock access to
->gp_flags.  Although it is hard to imagine any sane compiler messing
this particular case up, the documentation benefits are substantial.
Plus the definition of "sane compiler" grows ever looser.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 62b67b78b661..6d028fdbf86c 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1481,7 +1481,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
 		/* Handle grace-period start. */
 		for (;;) {
 			wait_event_interruptible(rsp->gp_wq,
-						 rsp->gp_flags &
+						 ACCESS_ONCE(rsp->gp_flags) &
 						 RCU_GP_FLAG_INIT);
 			if (rcu_gp_init(rsp))
 				break;