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

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Message-ID: <20081116062213.GA32215@elte.hu>
Date:	Sun, 16 Nov 2008 07:22:13 +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 3/4] tracing/branch-tracer: Fix a trace recursion on
	branch tracer


* 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
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