2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------
From: Will Deacon <will.dea...@arm.com>
[ upstream commit f4f38430c94c38187db73a2cf3892cc8b12a2713 ]
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: <sta...@kernel.org>
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: Andi Kleen <a...@linux.intel.com>
Index: linux-2.6.35.y/arch/arm/kernel/perf_event.c
===================================================================
--- linux-2.6.35.y.orig/arch/arm/kernel/perf_event.c
+++ linux-2.6.35.y/arch/arm/kernel/perf_event.c
@@ -531,7 +531,7 @@ void
hw_perf_enable(void)
{
/* 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)
@@ -544,9 +544,11 @@ hw_perf_enable(void)
continue;
armpmu->enable(&event->hw, idx);
+ enabled = 1;
}
- armpmu->start();
+ if (enabled)
+ armpmu->start();
}
void
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