linux-kernel - [PATCH] watchdog: avoid kernel crash when disabling watchdog

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Date:	Tue, 14 Sep 2010 15:34:01 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	linux-kernel@...r.kernel.org
Cc:	peterz@...radead.org, mingo@...e.hu, paulus@...ba.org,
	davem@...emloft.net, fweisbec@...il.com,
	perfmon2-devel@...ts.sf.net, eranian@...il.com, eranian@...gle.com,
	robert.richter@....com, dzickus@...hat.com
Subject: [PATCH] watchdog: avoid kernel crash when disabling watchdog

In case you boot with the watchdog disabled, i.e., nowatchdog, then,
if you try to disable it via /proc/sys/kernel/watchdog, you get
a kernel crash. The reason is that you are trying to cancel a hrtimer
which has never been initialized.

This patch fixes this by skipping execution of
watchdog_disable_all_cpus() when the watchdog is marked
disabled from boot.

Signed-off-by: Stephane Eranian <eranian@...gle.com>
--
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 69a3d44..f335067 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -473,6 +473,9 @@ static void watchdog_disable_all_cpus(void)
 {
 	int cpu;
 
+	if (no_watchdog)
+		return;
+
 	for_each_online_cpu(cpu)
 		watchdog_disable(cpu);
 
--
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