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From: Vince Weaver <vincent.weaver@maine.edu>
X-Google-Original-From: Vince Weaver <vince@vincent-weaver-1.umelst.maine.edu>
Date: Mon, 23 Feb 2015 22:33:05 -0500 (EST)
To: Peter Zijlstra <peterz@infradead.org>
cc: Vince Weaver <vincent.weaver@maine.edu>, linux-kernel@vger.kernel.org,
        Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@redhat.com>, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: perf: fuzzer gets CPU stuck in perf_callchain()
In-Reply-To: <20150219170311.GH21418@twins.programming.kicks-ass.net>
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References: <alpine.DEB.2.11.1502191149140.28751@vincent-weaver-1.umelst.maine.edu> <20150219170311.GH21418@twins.programming.kicks-ass.net>
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On Thu, 19 Feb 2015, Peter Zijlstra wrote:

> On Thu, Feb 19, 2015 at 11:54:40AM -0500, Vince Weaver wrote:
> 
> > [ 7938.802139]  [<ffffffff8115e114>] perf_tp_event+0xc4/0x210
> > [ 7938.861174]  [<ffffffff810b4f8a>] perf_trace_lock+0x12a/0x160
> > [ 7938.882197]  [<ffffffff810b7f10>] lock_release+0x130/0x260
> > [ 7938.888754]  [<ffffffff816c7474>] _raw_spin_unlock_irqrestore+0x24/0x40
> > [ 7938.896510]  [<ffffffff8107bb4d>] do_send_sig_info+0x5d/0x80
> > [ 7938.903240]  [<ffffffff811f69df>] send_sigio_to_task+0x12f/0x1a0
> > [ 7938.923894]  [<ffffffff811f71ce>] send_sigio+0xae/0x100
> > [ 7938.930132]  [<ffffffff811f72b7>] kill_fasync+0x97/0xf0
> > [ 7938.942707]  [<ffffffff8115d0b4>] perf_event_wakeup+0xd4/0xf0
> > [ 7938.956367]  [<ffffffff8115d103>] perf_pending_event+0x33/0x60
> > [ 7938.963199]  [<ffffffff8114e3fc>] irq_work_run_list+0x4c/0x80
> > [ 7938.969932]  [<ffffffff8114e448>] irq_work_run+0x18/0x40
> > [ 7938.976212]  [<ffffffff810196af>] smp_trace_irq_work_interrupt+0x3f/0xc0
> > [ 7938.983957]  [<ffffffff816c99bd>] trace_irq_work_interrupt+0x6d/0x80
> 
> Ah, it looks like the never ending irq_work..
> 
> Could you try this?

sorry for the delay. I managed to reproduce this problem again on 4.0-rc1, 
verified it was reproducible, then applied the patch below and I could no 
longer trigger the issue.

Tested-by: Vince Weaver <vincent.weaver@maine.edu>



> 
> ---
>  kernel/events/core.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index f04daabfd1cf..088e81ae43cb 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -4574,6 +4574,13 @@ static void perf_pending_event(struct irq_work *entry)
>  {
>  	struct perf_event *event = container_of(entry,
>  			struct perf_event, pending);
> +	int rctx;
> +
> +	rctx = perf_swevent_get_recursion_context();
> +	/*
> +	 * If we 'fail' here, that's OK, it means recursion is already disabled
> +	 * and we won't recurse 'further'.
> +	 */
>  
>  	if (event->pending_disable) {
>  		event->pending_disable = 0;
> @@ -4584,6 +4591,9 @@ static void perf_pending_event(struct irq_work *entry)
>  		event->pending_wakeup = 0;
>  		perf_event_wakeup(event);
>  	}
> +
> +	if (rctx >= 0)
> +		perf_swevent_put_recursion_context(rctx);
>  }
>  
>  /*
--
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