Messages in this thread Patch in this message | | | Date | Mon, 01 Aug 2011 16:18:32 -0700 | From | Greg KH <> | Subject | [17/70] ARM: 6989/1: perf: do not start the PMU when no events are present |
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2.6.39-stable review patch. If anyone has any objections, please let us know.
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From: Will Deacon <will.deacon@arm.com>
commit f4f38430c94c38187db73a2cf3892cc8b12a2713 upstream.
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.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/arm/kernel/perf_event.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/arch/arm/kernel/perf_event.c +++ b/arch/arm/kernel/perf_event.c @@ -588,7 +588,7 @@ static int armpmu_event_init(struct perf 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) @@ -601,9 +601,11 @@ static void armpmu_enable(struct pmu *pm continue; armpmu->enable(&event->hw, idx); + enabled = 1; } - armpmu->start(); + if (enabled) + armpmu->start(); } static void armpmu_disable(struct pmu *pmu)
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