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Date: Sat, 9 Nov 2013 16:59:38 +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
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On Sat, Nov 09, 2013 at 04:27:01PM +0100, Frederic Weisbecker wrote:
> In fact, raising an irq work from an irq work should simply be prohibited. That's not a sane
> behaviour.

Well, it is because as you raised on IRC we could be holding locks and
trying to avoid deadlocks. This is the very reason irq_work gets used in
printk.

And its not a recursive run()->work()->queue() either, because as you said this
tracepoint is in arch code _after_ work_run completes.

All in all an exceedingly vexing issue.