Commit f4f38430 authored Jul 01, 2011 by Will Deacon Committed by Russell King Jul 05, 2011

ARM: 6989/1: perf: do not start the PMU when no events are present



armpmu_enable can be called in situations where no events are present
(for example, from the event rotation tick after a profiled task has
exited). In this case, we currently start the PMU anyway which may
leave it active inevitably without any events being monitored.

This patch adds a simple check to the enabling code so that we avoid
starting the PMU when no events are present.

Cc: <stable@kernel.org>
Reported-by: Ashwin Chaugle <ashwinc@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

parent 17878362

arch/arm/kernel/perf_event.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -583,7 +583,7 @@ static int armpmu_event_init(struct perf_event *event)
		static void armpmu_enable(struct pmu *pmu)
		{
		/* Enable all of the perf events on hardware. */
		int idx;
		int idx, enabled = 0;
		struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);

		if (!armpmu)
		@@ -596,8 +596,10 @@ static void armpmu_enable(struct pmu *pmu)
		continue;

		armpmu->enable(&event->hw, idx);
		enabled = 1;
		}

		if (enabled)
		armpmu->start();
		}