linux-kernel - Re: perf/tracepoint: another fuzzer generated lockup

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Message-ID: <20131109151356.GA4971@laptop.programming.kicks-ass.net>
Date:	Sat, 9 Nov 2013 16:13:56 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Vince Weaver <vincent.weaver@...ne.edu>,
	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>, Dave Jones <davej@...hat.com>
Subject: Re: perf/tracepoint: another fuzzer generated lockup

On Sat, Nov 09, 2013 at 03:52:59PM +0100, Frederic Weisbecker wrote:
> So, an idea of what may be happening: an event overflows while FASYNC flag is set so it triggers an irq work
> to send the signal (kill_fasync).
> After the irq work triggers, it generates an irq_work_exit event, which in turn overflows and,
> if it has FASYNC, triggers a new irq work. The irq work triggers and generates an irq work exit event which
> has FASYNC flag, etc...
> 
> Looks like a nice way to deadlock with an infinite loop of irq work.


Yep, exactly, see the email I just send.
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