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Date: Mon, 23 Mar 2009 09:26:42 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, LKML <linux-kernel@vger.kernel.org>,
       Greg Kroah-Hartman <gregkh@suse.de>
Subject: Re: [PATCH 3/5] tracing/ftrace: check if debugfs is registered
	before creating files
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* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> Impact: fix a crash with ftrace={nop,boot} parameter
> 
> If the nop or initcall tracers are launched as boot tracers,
> they will attempt to create their option directory and files.
> But these tracers are registered very early and then assigned
> as "boot tracers" very early if asked to.
> 
> Since they do this before debugfs has been registered (core initcall),
> a crash is triggered.
> 
> Another early tracers could also come later. So we fix it by
> checking if debugfs is initialized before creating the root
> tracing directory.
> 
> Cc: Greg Kroah-Hartman <gregkh@suse.de>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> ---
>  kernel/trace/trace.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)

Note - i'll delay this patch pending Greg's Ack.

	Ingo