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Subject: Re: PATCH? trace_remove_event_call() should fail if call is active
From: Steven Rostedt <rostedt@goodmis.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        "zhangwei(Jovi)" <jovi.zhangwei@huawei.com>,
        Jiri Olsa <jolsa@redhat.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org
Date: Wed, 03 Jul 2013 14:02:27 -0400
In-Reply-To: <20130703175420.GA25668@redhat.com>
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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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