From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932577AbZGRHRO (ORCPT ); Sat, 18 Jul 2009 03:17:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932532AbZGRHRM (ORCPT ); Sat, 18 Jul 2009 03:17:12 -0400 Received: from mail-qy0-f198.google.com ([209.85.221.198]:33018 "EHLO mail-qy0-f198.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932459AbZGRHRG (ORCPT ); Sat, 18 Jul 2009 03:17:06 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:cc:subject:date:message-id:x-mailer:in-reply-to:references; b=sdAjinVkO7nm9BleE5TM/KOvNGHOLq2T7D70WOxWkwph7Z+S+z4Wq0tPonT2vFh/Cq Nt0nfGE7Gz6N5ikXWqi4IPNqxwDVp8RYH1YhlbUhiLfzLoFk9jMGUi8yhBfwK3lgZZiF QfodnhshanH2aUS2oDr3VRy1/GJTJlWjf9Yss= From: Frederic Weisbecker To: Ingo Molnar , Thomas Gleixner Cc: LKML , Lai Jiangshan , Steven Rostedt , Xiao Guangrong , Frederic Weisbecker Subject: [PATCH 1/4] ring_buffer: Fix warning while ignoring cmpxchg return value Date: Sat, 18 Jul 2009 03:16:58 -0400 Message-Id: <1247901421-6389-2-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.6.2.3 In-Reply-To: <1247901421-6389-1-git-send-email-fweisbec@gmail.com> References: <1247901421-6389-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan 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, because we don't need here to handle the fail case of cmpxchg, it's fine if an interrupt already did the job. Changed from V1: Add a comment(which is written by Steven) for it. Signed-off-by: Lai Jiangshan Acked-by: Steven Rostedt Signed-off-by: Frederic Weisbecker --- kernel/trace/ring_buffer.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) 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. -- 1.6.2.3