Commit e5302920 authored Jul 05, 2013 by Stephane Eranian Committed by Ingo Molnar Jul 05, 2013

perf: Fix interrupt handler timing harness



This patch fixes a serious bug in:

  14c63f17 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>

parent 100ac533

kernel/events/core.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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;