From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752875AbZGOI06 (ORCPT ); Wed, 15 Jul 2009 04:26:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752196AbZGOI05 (ORCPT ); Wed, 15 Jul 2009 04:26:57 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:56369 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752546AbZGOI05 (ORCPT ); Wed, 15 Jul 2009 04:26:57 -0400 Message-ID: <4A5D92F2.1010007@cn.fujitsu.com> Date: Wed, 15 Jul 2009 16:27:30 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Ingo Molnar , Steven Rostedt , Frederic Weisbecker , LKML Subject: [PATCH -tip V2] ring_buffer: fix warning References: <4A5C3549.7000905@cn.fujitsu.com> <4A5D90B1.3020304@cn.fujitsu.com> In-Reply-To: <4A5D90B1.3020304@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Sorry for missing Reviewed-by and Acked-by, so I resend it. Subject: [PATCH -tip V2] ring_buffer: fix warning kernel/trace/ring_buffer.c: In function 'rb_tail_page_update': kernel/trace/ring_buffer.c:849: warning: value computed is not used kernel/trace/ring_buffer.c:850: warning: value computed is not used Add "(void)"s to fix this warning. Changed from V1: Add a comment(which is written by Steven) for it. Signed-off-by: Lai Jiangshan Reviewed-by: Frederic Weisbecker Acked-by: Steven Rostedt --- diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index e648ba4..51633d7 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -845,9 +845,14 @@ static int rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, * This will only succeed if an interrupt did * not come in and change it. In which case, we * do not want to modify it. + * + * We add (void) to let the compiler know that we do not care + * about the return value of these functions. We use the + * cmpxchg to only update if an interrupt did not already + * do it for us. If the cmpxchg fails, we don't care. */ - local_cmpxchg(&next_page->write, old_write, val); - local_cmpxchg(&next_page->entries, old_entries, eval); + (void)local_cmpxchg(&next_page->write, old_write, val); + (void)local_cmpxchg(&next_page->entries, old_entries, eval); /* * No need to worry about races with clearing out the commit.