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    Subject[PATCH 3.18 112/144] perf: Fix PERF_EVENT_IOC_PERIOD deadlock
    Date
    3.18-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    [ Upstream commit 642c2d671ceff40e9453203ea0c66e991e11e249 ]

    Dmitry reported a fairly silly recursive lock deadlock for
    PERF_EVENT_IOC_PERIOD, fix this by explicitly doing the inactive part of
    __perf_event_period() instead of calling that function.

    Reported-by: Dmitry Vyukov <dvyukov@google.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: <stable@vger.kernel.org>
    Cc: Alexander Potapenko <glider@google.com>
    Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Eric Dumazet <edumazet@google.com>
    Cc: Jiri Olsa <jolsa@redhat.com>
    Cc: Kostya Serebryany <kcc@google.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Sasha Levin <sasha.levin@oracle.com>
    Cc: Stephane Eranian <eranian@google.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Vince Weaver <vincent.weaver@maine.edu>
    Fixes: c7999c6f3fed ("perf: Fix PERF_EVENT_IOC_PERIOD migration race")
    Link: http://lkml.kernel.org/r/20151130115615.GJ17308@twins.programming.kicks-ass.net
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/events/core.c | 9 ++++++++-
    1 file changed, 8 insertions(+), 1 deletion(-)

    diff --git a/kernel/events/core.c b/kernel/events/core.c
    index 1f08f691de59..7b2f9d432fe7 100644
    --- a/kernel/events/core.c
    +++ b/kernel/events/core.c
    @@ -3929,7 +3929,14 @@ retry:
    goto retry;
    }

    - __perf_event_period(&pe);
    + if (event->attr.freq) {
    + event->attr.sample_freq = value;
    + } else {
    + event->attr.sample_period = value;
    + event->hw.sample_period = value;
    + }
    +
    + local64_set(&event->hw.period_left, 0);
    raw_spin_unlock_irq(&ctx->lock);

    return 0;
    --
    2.17.1


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