linux-kernel - Re: [PATCH 2/2] tracing: use nowakeup version of commit for function event trace tests

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Message-ID: <20090420224129.GB5997@nowhere>
Date:	Tue, 21 Apr 2009 00:41:30 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/2] tracing: use nowakeup version of commit for
	function event trace tests

On Mon, Apr 20, 2009 at 06:22:59PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <srostedt@...hat.com>
> 
> The startup tests for the event tracer also runs with the function
> tracer enabled. The "wakeup" version of the trace commit was used
> which can grab spinlocks. If a task was preempted by an NMI
> that called a function being traced, it could deadlock due to the
> function tracer trying to grab the same lock.
> 
> Thanks to Frederic Weisbecker for pointing out where the bug was.
> 
> Reported-by: Ingo Molnar <mingo@...e.hu>
> Reported-by: Frederic Weisbecker <fweisbec@...il.com>
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> ---


Aah, I was about to push my version, which was the same but with
a more weird changelog :-)

Frederic.



>  kernel/trace/trace_events.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 98daf5d..672b195 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -1164,7 +1164,7 @@ function_test_events_call(unsigned long ip, unsigned long parent_ip)
>  	entry->ip			= ip;
>  	entry->parent_ip		= parent_ip;
>  
> -	trace_current_buffer_unlock_commit(event, flags, pc);
> +	trace_nowake_buffer_unlock_commit(event, flags, pc);
>  
>   out:
>  	atomic_dec(&per_cpu(test_event_disable, cpu));
> -- 
> 1.6.2.1
> 
> -- 
> --
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