From: James Hogan <james.hogan@imgtec.com>
Date: Wed, 27 Feb 2013 16:16:38 +0000 (+0000)
Subject: metag: perf: fix wrap handling in delta calculation
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=c43ca04b5e7854b3996f84a495e4553941e76266;p=linux-beck.git

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>
---

diff --git a/arch/metag/kernel/perf/perf_event.c b/arch/metag/kernel/perf/perf_event.c
index f38bf6d4dc55..8096db2a550b 100644
--- a/arch/metag/kernel/perf/perf_event.c
+++ b/arch/metag/kernel/perf/perf_event.c
@@ -211,7 +211,7 @@ again:
 	/*
 	 * 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);
 }