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Date: Sat, 9 Nov 2013 16:13:56 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Vince Weaver <vincent.weaver@maine.edu>,
        Steven Rostedt <rostedt@goodmis.org>,
        LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Dave Jones <davej@redhat.com>
Subject: Re: perf/tracepoint: another fuzzer generated lockup
Message-ID: <20131109151356.GA4971@laptop.programming.kicks-ass.net>
References: <alpine.DEB.2.10.1311081440440.7281@vincent-weaver-1.um.maine.edu>
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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.