linux-kernel - Re: PATCH? trace_remove_event_call() should fail if call is active

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Date:	Wed, 03 Jul 2013 14:02:27 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"zhangwei(Jovi)" <jovi.zhangwei@...wei.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: PATCH? trace_remove_event_call() should fail if call is active

On Wed, 2013-07-03 at 19:54 +0200, Oleg Nesterov wrote:
> On 07/03, Oleg Nesterov wrote:
> >
> > IOW. So far _I think_ we just need the additional changes in
> > trace_remove_event_call() if it succeeds (with the patch I sent)
> > to prevent the races like above, but I didn't even try to think
> > about this problem.
> 
> And I guess greatly underestimated the problem(s). When I look at
> this code now, it seems that, say, event_enable_write() will use
> the already freed ftrace_event_file in this case.
> 
> Still I think this is another (although closely related) problem.

Correct, and I think if we fix that problem, it will encapsulate fixing
the kprobe race too.

-- Steve


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