From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com,
edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com,
sbw@mit.edu, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 03/10] rcu: Flag lockless access to ->gp_flags with ACCESS_ONCE()
Date: Tue, 24 Sep 2013 18:42:32 -0700 [thread overview]
Message-ID: <1380073359-31959-3-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <1380073359-31959-1-git-send-email-paulmck@linux.vnet.ibm.com>
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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>
---
kernel/rcutree.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 62b67b7..6d028fd 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;
--
1.8.1.5
next prev parent reply other threads:[~2013-09-25 1:42 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-25 1:42 [PATCH tip/core/rcu 0/10] Grace-period-related changes for 3.13 Paul E. McKenney
2013-09-25 1:42 ` [PATCH tip/core/rcu 01/10] rcu: Improve grace-period start logic Paul E. McKenney
2013-09-25 1:42 ` [PATCH tip/core/rcu 02/10] rcu: Prevent spurious-wakeup DoS attack on rcu_gp_kthread() Paul E. McKenney
2013-09-25 1:42 ` Paul E. McKenney [this message]
2013-09-25 1:42 ` [PATCH tip/core/rcu 04/10] rcu: Add tracing to rcu_gp_kthread() Paul E. McKenney
2013-09-25 1:42 ` [PATCH tip/core/rcu 05/10] rcu: Add tracing of normal (non-NOCB) grace-period requests Paul E. McKenney
2013-09-25 1:42 ` [PATCH tip/core/rcu 06/10] rcu: Add tracing for rcuo no-CBs CPU wakeup handshake Paul E. McKenney
2013-09-25 1:42 ` [PATCH tip/core/rcu 07/10] rcu: Distinguish between NOCB and non-NOCB rcu_callback trace events Paul E. McKenney
2013-09-25 1:42 ` [PATCH tip/core/rcu 08/10] rcu: Track rcu_nocb_kthread()'s sleeping and awakening Paul E. McKenney
2013-09-25 1:42 ` [PATCH tip/core/rcu 09/10] rcu: Avoid sparse warnings in rcu_nocb_wake trace event Paul E. McKenney
2013-09-25 1:42 ` [PATCH tip/core/rcu 10/10] sched, rcu: Make RCU use resched_cpu() Paul E. McKenney
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