linux-kernel - Re: [PATCH v2] perf/core: fix a possible deadlock scenario

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Message-ID: <CAM_iQpV33dj-_bwYp3QJdPKihR8HyPzKMOpi1Lrqm7VtN3bZ8w@mail.gmail.com>
Date:   Mon, 23 Jul 2018 18:35:54 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>
Subject: Re: [PATCH v2] perf/core: fix a possible deadlock scenario

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!