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perf: Fix interrupt handler timing harness

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This patch fixes a serious bug in:

  14c63f17b1 perf: Drop sample rate when sampling is too slow

There was an misunderstanding on the API of the do_div()
macro. It returns the remainder of the division and this
was not what the function expected leading to disabling the
interrupt latency watchdog.

This patch also remove a duplicate assignment in
perf_sample_event_took().

Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Cc: dave.hansen@linux.intel.com
Cc: ak@linux.intel.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/20130704223010.GA30625@quad
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Stephane Eranian 2013-07-05 00:30:11 +02:00 committed by Ingo Molnar
parent 100ac53315
commit e5302920da
1 changed files with 2 additions and 2 deletions
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4
kernel/events/core.c
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@ -182,7 +182,7 @@ void update_perf_cpu_limits(void)
u64 tmp = perf_sample_period_ns;
tmp *= sysctl_perf_cpu_time_max_percent;
tmp = do_div(tmp, 100);
do_div(tmp, 100);
atomic_set(&perf_sample_allowed_ns, tmp);
}
@ -232,7 +232,7 @@ DEFINE_PER_CPU(u64, running_sample_length);
void perf_sample_event_took(u64 sample_len_ns)
{
u64 avg_local_sample_len;
u64 local_samples_len = __get_cpu_var(running_sample_length);
u64 local_samples_len;
if (atomic_read(&perf_sample_allowed_ns) == 0)
return;