[tip:perf/core] perf: Update a stale comment

[tip-bot for Peter Zijlstra <tipbot@zytor.com>]

Commit-ID:  394570b7939e1262f39373866166d8ee0a506e88
Gitweb:     http://git.kernel.org/tip/394570b7939e1262f39373866166d8ee0a506e88
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 31 Oct 2013 17:41:23 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 6 Nov 2013 12:34:23 +0100

perf: Update a stale comment

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Michael Neuling <mikey@neuling.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: james.hogan@imgtec.com
Cc: Vince Weaver <vince@deater.net>
Cc: Victor Kaplansky <VICTORK@il.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Anton Blanchard <anton@samba.org>
Link: http://lkml.kernel.org/n/tip-9s5mze78gmlz19agt39i8rii@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/events/ring_buffer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index c52a32f..e8b168a 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -85,8 +85,8 @@ again:
 	rb->user_page->data_head = head;
 
 	/*
-	 * Now check if we missed an update, rely on the (compiler)
-	 * barrier in atomic_dec_and_test() to re-read rb->head.
+	 * Now check if we missed an update -- rely on previous implied
+	 * compiler barriers to force a re-read.
 	 */
 	if (unlikely(head != local_read(&rb->head))) {
 		local_inc(&rb->nest);