| Message ID | 1345478941-32483-1-git-send-email-will.deacon@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c index ab243b8..29a6939 100644 --- a/arch/arm/kernel/perf_event.c +++ b/arch/arm/kernel/perf_event.c @@ -148,6 +148,10 @@ armpmu_event_set_period(struct perf_event *event, s64 period = hwc->sample_period; int ret = 0; + /* The period may have been changed by PERF_EVENT_IOC_PERIOD */ + if (unlikely(period != hwc->last_period)) + left = period - (hwc->last_period - left); + if (unlikely(left <= -period)) { left = period; local64_set(&hwc->period_left, left);
The PERF_EVENT_IOC_PERIOD ioctl command can be used to change the sample period of a running perf_event. Consequently, when calculating the next event period, the new period will only be considered after the previous one has overflowed. This patch changes the calculation of the remaining event ticks so that they are offset if the period has changed. Reported-by: Andreas Sandberg <andreas.sandberg@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> --- arch/arm/kernel/perf_event.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-)