linux-kernel - [tip:perf/urgent] watchdog: Don't throttle the watchdog

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Message-ID: <tip-c6db67cda735d8ace5f19c3831240e1408679790@git.kernel.org>
Date:	Mon, 23 Aug 2010 08:51:49 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, eranian@...gle.com, hpa@...or.com,
	mingo@...hat.com, a.p.zijlstra@...llo.nl, fweisbec@...il.com,
	tglx@...utronix.de, mingo@...e.hu, dzickus@...hat.com
Subject: [tip:perf/urgent] watchdog: Don't throttle the watchdog

Commit-ID:  c6db67cda735d8ace5f19c3831240e1408679790
Gitweb:     http://git.kernel.org/tip/c6db67cda735d8ace5f19c3831240e1408679790
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Fri, 20 Aug 2010 11:49:15 +0200
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Mon, 23 Aug 2010 10:48:05 +0200

watchdog: Don't throttle the watchdog

Stephane reported that when the machine locks up, the regular ticks,
which are responsible to resetting the throttle count, stop too.

Hence the NMI watchdog can end up being throttled before it reports on
the locked up state, and we end up being sad..

Cure this by having the watchdog overflow reset its own throttle count.

Reported-by: Stephane Eranian <eranian@...gle.com>
Tested-by: Stephane Eranian <eranian@...gle.com>
Cc: Don Zickus <dzickus@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <1282215916.1926.4696.camel@...top>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/watchdog.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 613bc1f..0d53c8e 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -206,6 +206,9 @@ void watchdog_overflow_callback(struct perf_event *event, int nmi,
 		 struct perf_sample_data *data,
 		 struct pt_regs *regs)
 {
+	/* Ensure the watchdog never gets throttled */
+	event->hw.interrupts = 0;
+
 	if (__get_cpu_var(watchdog_nmi_touch) == true) {
 		__get_cpu_var(watchdog_nmi_touch) = false;
 		return;
--
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