From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932144Ab0C3XRp (ORCPT ); Tue, 30 Mar 2010 19:17:45 -0400 Received: from kroah.org ([198.145.64.141]:51805 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756655Ab0C3XRg (ORCPT ); Tue, 30 Mar 2010 19:17:36 -0400 X-Mailbox-Line: From linux@linux.site Tue Mar 30 15:56:10 2010 Message-Id: <20100330225609.778211759@linux.site> User-Agent: quilt/0.47-14.9 Date: Tue, 30 Mar 2010 15:54:57 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Steven Rostedt , Greg Kroah-Hartman Subject: [019/116] tracing: Use same local variable when resetting the ring buffer In-Reply-To: <20100330230600.GA28802@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.32-stable review patch. If anyone has any objections, please let us know. ------------------ From: Steven Rostedt commit 283740c619d211e34572cc93c8cdba92ccbdb9cc upstream. In the ftrace code that resets the ring buffer it references the buffer with a local variable, but then uses the tr->buffer as the parameter to reset. If the wakeup tracer is running, which can switch the tr->buffer with the max saved buffer, this can break the requirement of disabling the buffer before the reset. buffer = tr->buffer; ring_buffer_record_disable(buffer); synchronize_sched(); __tracing_reset(tr->buffer, cpu); If the tr->buffer is swapped, then the reset is not happening to the buffer that was disabled. This will cause the ring buffer to fail. Found with Li Zefan's ftrace_stress_test. Reported-by: Lai Jiangshan Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -748,10 +748,10 @@ out: mutex_unlock(&trace_types_lock); } -static void __tracing_reset(struct trace_array *tr, int cpu) +static void __tracing_reset(struct ring_buffer *buffer, int cpu) { ftrace_disable_cpu(); - ring_buffer_reset_cpu(tr->buffer, cpu); + ring_buffer_reset_cpu(buffer, cpu); ftrace_enable_cpu(); } @@ -763,7 +763,7 @@ void tracing_reset(struct trace_array *t /* Make sure all commits have finished */ synchronize_sched(); - __tracing_reset(tr, cpu); + __tracing_reset(buffer, cpu); ring_buffer_record_enable(buffer); } @@ -781,7 +781,7 @@ void tracing_reset_online_cpus(struct tr tr->time_start = ftrace_now(tr->cpu); for_each_online_cpu(cpu) - __tracing_reset(tr, cpu); + __tracing_reset(buffer, cpu); ring_buffer_record_enable(buffer); }