From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758738Ab0CMC7z (ORCPT ); Fri, 12 Mar 2010 21:59:55 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:55803 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757759Ab0CMC65 (ORCPT ); Fri, 12 Mar 2010 21:58:57 -0500 X-Authority-Analysis: v=1.0 c=1 a=IvM2YAiW80kA:10 a=GzHTLUccyWwA:10 a=omOdbC7AAAAA:8 a=VwQbUJbxAAAA:8 a=meVymXHHAAAA:8 a=IC3tHotzItW5zZKPNX4A:9 a=IETZ_mQrS7iGj9heZukA:7 a=iXOPsagZIbTsr7gosu2E-H2WL-gA:4 a=LI9Vle30uBYA:10 a=jeBq3FmKZ4MA:10 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.89.75 Message-Id: <20100313025854.280882947@goodmis.org> User-Agent: quilt/0.48-1 Date: Fri, 12 Mar 2010 21:56:56 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Frederic Weisbecker , Li Zefan , Lai Jiangshan , stable@kernel.org Subject: [PATCH 1/5] ring-buffer: Move disabled check into preempt disable section References: <20100313025655.104950166@goodmis.org> Content-Disposition: inline; filename=0001-ring-buffer-Move-disabled-check-into-preempt-disable.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan 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)) -- 1.7.0