Commit 56cd0aef authored by Young Xiao's avatar Young Xiao Committed by David S. Miller

sparc: perf: fix updated event period in response to PERF_EVENT_IOC_PERIOD

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.

See commit 3581fe0e ("ARM: 7556/1: perf: fix updated event period in
response to PERF_EVENT_IOC_PERIOD") for details.
Signed-off-by: default avatarYoung Xiao <92siuyang@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 80caf435
...@@ -891,6 +891,10 @@ static int sparc_perf_event_set_period(struct perf_event *event, ...@@ -891,6 +891,10 @@ static int sparc_perf_event_set_period(struct perf_event *event,
s64 period = hwc->sample_period; s64 period = hwc->sample_period;
int ret = 0; 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)) { if (unlikely(left <= -period)) {
left = period; left = period;
local64_set(&hwc->period_left, left); local64_set(&hwc->period_left, left);
......
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