From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756823AbZDUOEV (ORCPT ); Tue, 21 Apr 2009 10:04:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752638AbZDUOEK (ORCPT ); Tue, 21 Apr 2009 10:04:10 -0400 Received: from hera.kernel.org ([140.211.167.34]:33363 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751542AbZDUOEI (ORCPT ); Tue, 21 Apr 2009 10:04:08 -0400 Date: Tue, 21 Apr 2009 14:03:29 GMT From: tip-bot for Steven Rostedt To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, rostedt@goodmis.org, srostedt@redhat.com, tglx@linutronix.de, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, rostedt@goodmis.org, srostedt@redhat.com, tglx@linutronix.de, mingo@elte.hu In-Reply-To: <20090421094616.GA14561@elte.hu> References: <20090421094616.GA14561@elte.hu> Subject: [tip:tracing/core] ring-buffer: only warn on wrap if buffer is bigger than two pages Message-ID: Git-Commit-ID: 3554228d4289098a8fe5cfd87512ec32a19bbe5a X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 21 Apr 2009 14:03:31 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 3554228d4289098a8fe5cfd87512ec32a19bbe5a Gitweb: http://git.kernel.org/tip/3554228d4289098a8fe5cfd87512ec32a19bbe5a Author: Steven Rostedt AuthorDate: Tue, 21 Apr 2009 09:41:26 -0400 Committer: Ingo Molnar CommitDate: Tue, 21 Apr 2009 16:00:45 +0200 ring-buffer: only warn on wrap if buffer is bigger than two pages On boot up, to save memory, ftrace allocates the minimum buffer which is two pages. Ftrace also goes through a series of tests (when configured) on boot up. These tests can fill up a page within a single interrupt. The ring buffer also has a WARN_ON when it detects that the buffer was completely filled within a single commit (other commits are allowed to be nested). Combine the small buffer on start up, with the tests that can fill more than a single page within an interrupt, this can trigger the WARN_ON. This patch makes the WARN_ON only happen when the ring buffer consists of more than two pages. [ Impact: prevent false WARN_ON in ftrace startup tests ] Reported-by: Ingo Molnar LKML-Reference: <20090421094616.GA14561@elte.hu> Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar --- kernel/trace/ring_buffer.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 7bcfd3e..61dbdf2 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1241,7 +1241,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, * about it. */ if (unlikely(next_page == commit_page)) { - WARN_ON_ONCE(1); + /* This can easily happen on small ring buffers */ + WARN_ON_ONCE(buffer->pages > 2); goto out_reset; }