[PATCH v12 1/8] arm64: arm_pmu: remove unnecessary isb instruction

Andrew Murray andrew.murray at arm.com
Thu Mar 28 03:37:24 PDT 2019

The armv8pmu_enable_event_counter function issues an isb instruction
after enabling a pair of counters - this doesn't provide any value
and is inconsistent with the armv8pmu_disable_event_counter.

In any case armv8pmu_enable_event_counter is always called with the
PMU stopped. Starting the PMU with armv8pmu_start results in an isb
instruction being issued prior to writing to PMCR_EL0.

Let's remove the unnecessary isb instruction.

Signed-off-by: Andrew Murray <andrew.murray at arm.com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose at arm.com>
Acked-by: Mark Rutland <mark.rutland at arm.com>
 arch/arm64/kernel/perf_event.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
index 4addb38bc250..cccf4fc86d67 100644
--- a/arch/arm64/kernel/perf_event.c
+++ b/arch/arm64/kernel/perf_event.c
@@ -533,7 +533,6 @@ static inline void armv8pmu_enable_event_counter(struct perf_event *event)
 	if (armv8pmu_event_is_chained(event))
 		armv8pmu_enable_counter(idx - 1);
-	isb();
 static inline int armv8pmu_disable_counter(int idx)

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