From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755593Ab0CMMZT (ORCPT ); Sat, 13 Mar 2010 07:25:19 -0500 Received: from hera.kernel.org ([140.211.167.34]:37743 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753183Ab0CMMZI (ORCPT ); Sat, 13 Mar 2010 07:25:08 -0500 Date: Sat, 13 Mar 2010 12:24:37 GMT From: tip-bot for Lai Jiangshan Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, rostedt@goodmis.org, lizf@cn.fujitsu.com, tglx@linutronix.de, laijs@cn.fujitsu.com Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, lizf@cn.fujitsu.com, rostedt@goodmis.org, tglx@linutronix.de, laijs@cn.fujitsu.com In-Reply-To: <4B949E43.2010906@cn.fujitsu.com> References: <4B949E43.2010906@cn.fujitsu.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:tracing/urgent] ring-buffer: Move disabled check into preempt disable section Message-ID: Git-Commit-ID: 52fbe9cde7fdb5c6fac196d7ebd2d92d05ef3cd4 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-4.2.3 (hera.kernel.org [127.0.0.1]); Sat, 13 Mar 2010 12:24:38 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 52fbe9cde7fdb5c6fac196d7ebd2d92d05ef3cd4 Gitweb: http://git.kernel.org/tip/52fbe9cde7fdb5c6fac196d7ebd2d92d05ef3cd4 Author: Lai Jiangshan AuthorDate: Mon, 8 Mar 2010 14:50:43 +0800 Committer: Steven Rostedt CommitDate: Fri, 12 Mar 2010 20:26:56 -0500 ring-buffer: Move disabled check into preempt disable section The ring buffer resizing and resetting relies on a schedule RCU action. The buffers are disabled, a synchronize_sched() is called and then the resize or reset takes place. But this only works if the disabling of the buffers are within the preempt disabled section, otherwise a window exists that the buffers can be written to while a reset or resize takes place. Cc: stable@kernel.org Reported-by: Li Zefan Signed-off-by: Lai Jiangshan LKML-Reference: <4B949E43.2010906@cn.fujitsu.com> Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 12 ++++++------ 1 files changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 8c1b2d2..54191d6 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -2232,12 +2232,12 @@ ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) if (ring_buffer_flags != RB_BUFFERS_ON) return NULL; - if (atomic_read(&buffer->record_disabled)) - return NULL; - /* If we are tracing schedule, we don't want to recurse */ resched = ftrace_preempt_disable(); + if (atomic_read(&buffer->record_disabled)) + goto out_nocheck; + if (trace_recursive_lock()) goto out_nocheck; @@ -2469,11 +2469,11 @@ int ring_buffer_write(struct ring_buffer *buffer, if (ring_buffer_flags != RB_BUFFERS_ON) return -EBUSY; - if (atomic_read(&buffer->record_disabled)) - return -EBUSY; - resched = ftrace_preempt_disable(); + if (atomic_read(&buffer->record_disabled)) + goto out; + cpu = raw_smp_processor_id(); if (!cpumask_test_cpu(cpu, buffer->cpumask))