linux-kernel - Re: [PATCH 3/4] tracing/branch-tracer: Fix a trace recursion on branch tracer

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Message-ID: <c62985530811152232q2794ce1o6732c241821c6eca@mail.gmail.com>
Date:	Sun, 16 Nov 2008 07:32:46 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Ingo Molnar" <mingo@...e.hu>
Cc:	"Steven Rostedt" <rostedt@...dmis.org>,
	"Linux Kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] tracing/branch-tracer: Fix a trace recursion on branch tracer

2008/11/16 Ingo Molnar <mingo@...e.hu>:
>
> * Frederic Weisbecker <fweisbec@...il.com> wrote:
>
>> Impact: Make the branch tracer use raw irq save/restore
>>
>> When the branch tracer inserts an event through
>> probe_likely_condition(), it calls local_irq_save() and then results
>> in a trace recursion.
>>
>> local_irq_save() -> trace_hardirqs_off() -> trace_hardirqs_off_caller()
>>       -> unlikely()
>>
>> The trace_branch.c file is protected by DISABLE_BRANCH_PROFILING but
>> that doesn't prevent from external call to functions that use
>> unlikely().
>>
>> My box crashed each time I tried to set this tracer (sudden and hard
>> reboot).
>
> So this patch fixes that problem, or are there other problems left?
>
>        Ingo
>


I forgot to answer to all. Yes that fixes it.
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