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Subject[PATCH 1/3] watchdog: Fix broken nowatchdog logic
Date
From: Marcin Slusarz <marcin.slusarz@gmail.com>

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>
Cc: 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>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: stable@kernel.org
[ removed another no_watchdog instance ]
Signed-off-by: Don Zickus <dzickus@redhat.com>
---
kernel/watchdog.c | 20 ++++++--------------
1 files changed, 6 insertions(+), 14 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index aaa8dae..7d4213e 100644
--- 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, hrtimer_interrupts_saved);
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:
@@ -58,7 +55,7 @@ static int __init hardlockup_panic_setup(char *str)
if (!strncmp(str, "panic", 5))
hardlockup_panic = 1;
else if (!strncmp(str, "0", 1))
- no_watchdog = 1;
+ watchdog_enabled = 0;
return 1;
}
__setup("nmi_watchdog=", hardlockup_panic_setup);
@@ -77,7 +74,7 @@ __setup("softlockup_panic=", softlockup_panic_setup);

static int __init nowatchdog_setup(char *str)
{
- no_watchdog = 1;
+ watchdog_enabled = 0;
return 1;
}
__setup("nowatchdog", nowatchdog_setup);
@@ -85,7 +82,7 @@ __setup("nowatchdog", nowatchdog_setup);
/* deprecated */
static int __init nosoftlockup_setup(char *str)
{
- no_watchdog = 1;
+ watchdog_enabled = 0;
return 1;
}
__setup("nosoftlockup", nosoftlockup_setup);
@@ -476,9 +473,6 @@ static void watchdog_disable_all_cpus(void)
{
int cpu;

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

@@ -530,7 +524,8 @@ cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu)
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:
@@ -555,9 +550,6 @@ void __init lockup_detector_init(void)
void *cpu = (void *)(long)smp_processor_id();
int err;

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

--
1.7.3.4


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