[tip:perf/core] watchdog: Avoid kernel crash when disabling watchdog

[tip-bot for Stephane Eranian <eranian@google.com>]

Commit-ID:  d9ca07a05ce1c42ac9717e54eaea4546a3a80978
Gitweb:     http://git.kernel.org/tip/d9ca07a05ce1c42ac9717e54eaea4546a3a80978
Author:     Stephane Eranian <eranian@google.com>
AuthorDate: Tue, 14 Sep 2010 15:34:01 +0200
Committer:  Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 15 Sep 2010 10:43:58 +0200

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@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4c8f7a23.cae9d80a.2c11.0bb4@mx.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 kernel/watchdog.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index fa71aeb..89eadbb 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);