linux-kernel - Re: [PATCH] tracing: Fix infinite loop in ftrace_update_pid

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Message-ID: <20090929095133.GB6934@console-pimps.org>
Date:	Tue, 29 Sep 2009 10:51:33 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	linux-kernel@...r.kernel.org
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] tracing: Fix infinite loop in ftrace_update_pid_func()

On Mon, Sep 28, 2009 at 04:43:01PM +0100, Matt Fleming wrote:
> From: Matt Fleming <matthew.fleming@...tec.com>
> 
> When CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST is enabled
> __ftrace_trace_function contains the current trace function, not
> ftrace_trace_function. In ftrace_update_pid_func() we currently
> incorrectly assign the value of ftrace_trace_function to
> __ftrace_trace_funcion before returning.
> 
> Without this patch it is possible to execute an infinite loop whereby
> ftrace_test_stop_func() calls __ftrace_trace_function, which was
> assigned ftrace_test_stop_func() in ftrace_update_pid_func().
> 

Oops..

I just realised I've used the phrase "infinite loop" when what I meant
to say was "infinite recursion". Sorry, brain fart.
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