linux-kernel - [PATCH] perf: fix possible divide-by-zero in perf_swevent

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Message-Id: <1282824438-13970-1-git-send-email-dongdong.deng@windriver.com>
Date:	Thu, 26 Aug 2010 20:07:18 +0800
From:	Dongdong Deng <dongdong.deng@...driver.com>
To:	mingo@...e.hu, a.p.zijlstra@...llo.nl, fweisbec@...il.com
Cc:	acme@...hat.com, paulus@...ba.org, linux-kernel@...r.kernel.org
Subject: [PATCH] perf: fix possible divide-by-zero in perf_swevent_overflow()

The event->hw.last_period is possible to zero, thus it will
cause divide_by_zero later in perf_swevent_set_period().

This patch checks event->hw.last_period before invoke
perf_swevent_set_period() and replaces "event->hw" with "hwc".

Signed-off-by: Dongdong Deng <dongdong.deng@...driver.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Paul Mackerras <paulus@...ba.org>
---
 kernel/perf_event.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 403d180..ccba741 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -4050,8 +4050,8 @@ static void perf_swevent_overflow(struct perf_event *event, u64 overflow,
 	struct hw_perf_event *hwc = &event->hw;
 	int throttle = 0;
 
-	data->period = event->hw.last_period;
-	if (!overflow)
+	data->period = hwc->last_period;
+	if (!overflow && hwc->last_period)
 		overflow = perf_swevent_set_period(event);
 
 	if (hwc->interrupts == MAX_INTERRUPTS)
-- 
1.6.0.4

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