linux-kernel - Re: [PATCH] tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time

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Date:	Tue, 16 Dec 2008 22:20:28 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/ftrace: use preempt_enable_no_resched_notrace
	in ring_buffer_time_stamp()


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> Impact: prevent a trace recursion
> 
> After some tests with function graph tracer under x86-32, I saw some recursions
> caused by ring_buffer_time_stamp() that calls preempt_enable_no_notrace() which
> calls preempt_schedule() which is traced itself.
> 
> This patch re-enables preemption without rescheduling.
> 
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> ---
>  kernel/trace/ring_buffer.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)

applied to tip/tracing/ftrace, thanks Frederic!

Does this explain+fix the weird crashes/reboots you were seeing?

	Ingo
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