Commit c43ca04b authored Feb 27, 2013 by James Hogan

metag: perf: fix wrap handling in delta calculation

When calculating the delta, mask with MAX_PERIOD (24 bits) to handle
wrapping, which particularly happens with periodic sampling since the
value is intentionally set so that it will overflow soon.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>

parent 3424dabb

arch/metag/kernel/perf/perf_event.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -211,7 +211,7 @@ void metag_pmu_event_update(struct perf_event *event,
		/*
		* Calculate the delta and add it to the counter.
		*/
		delta = new_raw_count - prev_raw_count;
		delta = (new_raw_count - prev_raw_count) & MAX_PERIOD;

		local64_add(delta, &event->count);
		}