From: Peter Zijlstra <[email protected]> Vince Weaver reports that, on all architectures apart from ARM, PERF_EVENT_IOC_PERIOD doesn't actually update the period until the next event fires. This is counter-intuitive behaviour and is better dealt with in the core code.
This patch ensures that the period is forcefully reset when dealing with such a request in the core code. A subsequent patch removes the equivalent hack from the ARM back-end. Cc: Vince Weaver <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Will Deacon <[email protected]> --- Peter -- I didn't want this to get lost, so I picked it up, fixed a typo and wrote a commit message. Could I add your SoB please? Cheers, Will kernel/events/core.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index d724e7757cd1..1c626b923ddf 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3527,7 +3527,7 @@ static void perf_event_for_each(struct perf_event *event, static int perf_event_period(struct perf_event *event, u64 __user *arg) { struct perf_event_context *ctx = event->ctx; - int ret = 0; + int ret = 0, active; u64 value; if (!is_sampling_event(event)) @@ -3551,6 +3551,20 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg) event->attr.sample_period = value; event->hw.sample_period = value; } + + active = (event->state == PERF_EVENT_STATE_ACTIVE); + if (active) { + perf_pmu_disable(ctx->pmu); + event->pmu->stop(event, PERF_EF_UPDATE); + } + + local64_set(&event->hw.period_left, 0); + + if (active) { + event->pmu->start(event, PERF_EF_RELOAD); + perf_pmu_enable(ctx->pmu); + } + unlock: raw_spin_unlock_irq(&ctx->lock); -- 1.8.2.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
