Skip to content

Commit

Permalink
perf: Fix PERF_EVENT_IOC_PERIOD to force-reset the period
Browse files Browse the repository at this point in the history
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.

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Link: http://lkml.kernel.org/r/1385560479-11014-1-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
  • Loading branch information
Peter Zijlstra authored and Ingo Molnar committed Dec 17, 2013
1 parent 7fd565e commit bad7192
Showing 1 changed file with 15 additions and 1 deletion.
16 changes: 15 additions & 1 deletion kernel/events/core.c
Original file line number Diff line number Diff line change
Expand Up @@ -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))
Expand All @@ -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);

Expand Down

0 comments on commit bad7192

Please sign in to comment.