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Subject[229/272] watchdog: Fix broken nowatchdog logic
2.6.37-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Marcin Slusarz <marcin.slusarz@gmail.com>

commit 4135038a582c20ffdadfcf6564852e0b72a20968 upstream.

Passing nowatchdog to kernel disables 2 things: creation of
watchdog threads AND initialization of percpu watchdog_hrtimer.
As hrtimers are initialized only at boot it's not possible to
enable watchdog later - for me all watchdog threads started to
eat 100% of CPU time, but they could just crash.

Additionally, even if these threads would start properly,
watchdog_disable_all_cpus was guarded by no_watchdog check, so
you couldn't disable watchdog.

To fix this, remove no_watchdog variable and use already
existing watchdog_enabled variable.

Signed-off-by: Marcin Slusarz <marcin.slusarz@gmail.com>
[ removed another no_watchdog instance ]
Signed-off-by: Don Zickus <dzickus@redhat.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1296230433-6261-1-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/watchdog.c | 18 +++++-------------
1 file changed, 5 insertions(+), 13 deletions(-)

--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -27,7 +27,7 @@
#include <asm/irq_regs.h>
#include <linux/perf_event.h>

-int watchdog_enabled;
+int watchdog_enabled = 1;
int __read_mostly softlockup_thresh = 60;

static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
@@ -43,9 +43,6 @@ static DEFINE_PER_CPU(unsigned long, hrt
static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
#endif

-static int no_watchdog;
-
-
/* boot commands */
/*
* Should we panic when a soft-lockup or hard-lockup occurs:
@@ -75,7 +72,7 @@ __setup("softlockup_panic=", softlockup_

static int __init nowatchdog_setup(char *str)
{
- no_watchdog = 1;
+ watchdog_enabled = 0;
return 1;
}
__setup("nowatchdog", nowatchdog_setup);
@@ -83,7 +80,7 @@ __setup("nowatchdog", nowatchdog_setup);
/* deprecated */
static int __init nosoftlockup_setup(char *str)
{
- no_watchdog = 1;
+ watchdog_enabled = 0;
return 1;
}
__setup("nosoftlockup", nosoftlockup_setup);
@@ -475,9 +472,6 @@ static void watchdog_disable_all_cpus(vo
{
int cpu;

- if (no_watchdog)
- return;
-
for_each_online_cpu(cpu)
watchdog_disable(cpu);

@@ -531,7 +525,8 @@ cpu_callback(struct notifier_block *nfb,
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
- err = watchdog_enable(hotcpu);
+ if (watchdog_enabled)
+ err = watchdog_enable(hotcpu);
break;
#ifdef CONFIG_HOTPLUG_CPU
case CPU_UP_CANCELED:
@@ -556,9 +551,6 @@ static int __init spawn_watchdog_task(vo
void *cpu = (void *)(long)smp_processor_id();
int err;

- if (no_watchdog)
- return 0;
-
err = cpu_callback(&cpu_nfb, CPU_UP_PREPARE, cpu);
WARN_ON(notifier_to_errno(err));




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