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>

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index fa71aeb..89eadbb 100644 (file)
--- 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);