2.6.39-stable review patch. If anyone has any objections, please let us know.
------------------
From: Will Deacon <will.dea...@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 <ashw...@codeaurora.org>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Russell King <rmk+ker...@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gre...@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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