Commit 642c2d67 authored Nov 30, 2015 by Peter Zijlstra Committed by Ingo Molnar Dec 04, 2015

perf: Fix PERF_EVENT_IOC_PERIOD deadlock



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: c7999c6f ("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>

parent 90eec103

kernel/events/core.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -4225,7 +4225,14 @@ static int perf_event_period(struct perf_event event, u64 __user arg)
		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;