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-rw-r--r--arch/arm/kernel/perf_event.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index f7c65adaa42..557e128e4df 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -116,8 +116,14 @@ int armpmu_event_set_period(struct perf_event *event)
ret = 1;
}
- if (left > (s64)armpmu->max_period)
- left = armpmu->max_period;
+ /*
+ * Limit the maximum period to prevent the counter value
+ * from overtaking the one we are about to program. In
+ * effect we are reducing max_period to account for
+ * interrupt latency (and we are being very conservative).
+ */
+ if (left > (armpmu->max_period >> 1))
+ left = armpmu->max_period >> 1;
local64_set(&hwc->prev_count, (u64)-left);