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From: Cong Wang <xiyou.wangcong@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
	Andi Kleen <ak@linux.intel.com>
Subject: Re: [PATCH v2] perf/core: fix a possible deadlock scenario
Date: Mon, 23 Jul 2018 18:35:54 -0700	[thread overview]
Message-ID: <CAM_iQpV33dj-_bwYp3QJdPKihR8HyPzKMOpi1Lrqm7VtN3bZ8w@mail.gmail.com> (raw)
In-Reply-To: <CAM_iQpWVhLZKo9j6COGkvryGrxJq6sEXzh2S-ikza2H3=pAyqw@mail.gmail.com>

Hi, Peter, Andi

While reviewing the deadlock, I find out it looks like we could have the
following infinite recursion too:

perf_event_account_interrupt()
__perf_event_account_interrupt()
perf_adjust_period()
event->pmu->stop
x86_pmu_stop()
x86_pmu.disable()
intel_pmu_disable_event()
intel_pmu_pebs_disable()
intel_pmu_drain_pebs_buffer()
intel_pmu_drain_pebs_nhm()
<repeat....>

This time is pure hardware events, attr.freq must be non-zero.

And, we could enter this infinite recursion in NMI handler too:

intel_pmu_handle_irq()
perf_event_overflow()
__perf_event_overflow()
__perf_event_account_interrupt()
....

Or this is impossible too?

Thanks!

  reply	other threads:[~2018-07-24  1:39 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-16 21:51 [PATCH] perf/core: fix a possible deadlock scenario Cong Wang
2018-07-18  8:19 ` Jiri Olsa
2018-07-18 20:21   ` Cong Wang
2018-07-19 13:28     ` Jiri Olsa
2018-07-19 19:12       ` [PATCH v2] " Cong Wang
2018-07-20 11:52         ` Peter Zijlstra
2018-07-23 23:16           ` Cong Wang
2018-07-24  1:35             ` Cong Wang [this message]
2018-07-24  1:44               ` Cong Wang
2018-07-24  9:18                 ` Peter Zijlstra
2018-07-25 18:44                   ` Cong Wang
2018-07-24  9:12             ` Peter Zijlstra

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