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

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[ Upstream commit 56cd0aefa4 ]

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 3581fe0ef3 ("ARM: 7556/1: perf: fix updated event period in
response to PERF_EVENT_IOC_PERIOD") for details.

Signed-off-by: Young Xiao <92siuyang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Young Xiao 2019-05-29 10:21:48 +08:00 committed by Greg Kroah-Hartman
parent 7b460a9bb1
commit 16cdab6398
1 changed files with 4 additions and 0 deletions
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4
arch/sparc/kernel/perf_event.c
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@ -891,6 +891,10 @@ static int sparc_perf_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);