1 files changed, 47 insertions, 40 deletions

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 05039e348f07..52c9a9b91bdd 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -31,7 +31,7 @@
 
 int watchdog_enabled = 1;
 int __read_mostly watchdog_thresh = 10;
-static int __read_mostly watchdog_disabled;
+static int __read_mostly watchdog_disabled = 1;
 static u64 __read_mostly sample_period;
 
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
@@ -347,11 +347,6 @@ static void watchdog_enable(unsigned int cpu)
 	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	hrtimer->function = watchdog_timer_fn;
 
-	if (!watchdog_enabled) {
-		kthread_park(current);
-		return;
-	}
-
 	/* Enable the perf event */
 	watchdog_nmi_enable(cpu);
 
@@ -374,6 +369,11 @@ static void watchdog_disable(unsigned int cpu)
 	watchdog_nmi_disable(cpu);
 }
 
+static void watchdog_cleanup(unsigned int cpu, bool online)
+{
+	watchdog_disable(cpu);
+}
+
 static int watchdog_should_run(unsigned int cpu)
 {
 	return __this_cpu_read(hrtimer_interrupts) !=
@@ -475,28 +475,40 @@ static int watchdog_nmi_enable(unsigned int cpu) { return 0; }
 static void watchdog_nmi_disable(unsigned int cpu) { return; }
 #endif /* CONFIG_HARDLOCKUP_DETECTOR */
 
-/* prepare/enable/disable routines */
-/* sysctl functions */
-#ifdef CONFIG_SYSCTL
-static void watchdog_enable_all_cpus(void)
+static struct smp_hotplug_thread watchdog_threads = {
+	.store			= &softlockup_watchdog,
+	.thread_should_run	= watchdog_should_run,
+	.thread_fn		= watchdog,
+	.thread_comm		= "watchdog/%u",
+	.setup			= watchdog_enable,
+	.cleanup		= watchdog_cleanup,
+	.park			= watchdog_disable,
+	.unpark			= watchdog_enable,
+};
+
+static int watchdog_enable_all_cpus(void)
 {
-	unsigned int cpu;
+	int err = 0;
 
 	if (watchdog_disabled) {
-		watchdog_disabled = 0;
-		for_each_online_cpu(cpu)
-			kthread_unpark(per_cpu(softlockup_watchdog, cpu));
+		err = smpboot_register_percpu_thread(&watchdog_threads);
+		if (err)
+			pr_err("Failed to create watchdog threads, disabled\n");
+		else
+			watchdog_disabled = 0;
 	}
+
+	return err;
 }
 
+/* prepare/enable/disable routines */
+/* sysctl functions */
+#ifdef CONFIG_SYSCTL
 static void watchdog_disable_all_cpus(void)
 {
-	unsigned int cpu;
-
 	if (!watchdog_disabled) {
 		watchdog_disabled = 1;
-		for_each_online_cpu(cpu)
-			kthread_park(per_cpu(softlockup_watchdog, cpu));
+		smpboot_unregister_percpu_thread(&watchdog_threads);
 	}
 }
 
@@ -507,14 +519,14 @@ static void watchdog_disable_all_cpus(void)
 int proc_dowatchdog(struct ctl_table *table, int write,
 		    void __user *buffer, size_t *lenp, loff_t *ppos)
 {
-	int ret;
+	int err, old_thresh, old_enabled;
 
-	if (watchdog_disabled < 0)
-		return -ENODEV;
+	old_thresh = ACCESS_ONCE(watchdog_thresh);
+	old_enabled = ACCESS_ONCE(watchdog_enabled);
 
-	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
-	if (ret || !write)
-		return ret;
+	err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+	if (err || !write)
+		return err;
 
 	set_sample_period();
 	/*
@@ -523,29 +535,24 @@ int proc_dowatchdog(struct ctl_table *table, int write,
 	 * watchdog_*_all_cpus() function takes care of this.
 	 */
 	if (watchdog_enabled && watchdog_thresh)
-		watchdog_enable_all_cpus();
+		err = watchdog_enable_all_cpus();
 	else
 		watchdog_disable_all_cpus();
 
-	return ret;
+	/* Restore old values on failure */
+	if (err) {
+		watchdog_thresh = old_thresh;
+		watchdog_enabled = old_enabled;
+	}
+
+	return err;
 }
 #endif /* CONFIG_SYSCTL */
 
-static struct smp_hotplug_thread watchdog_threads = {
-	.store			= &softlockup_watchdog,
-	.thread_should_run	= watchdog_should_run,
-	.thread_fn		= watchdog,
-	.thread_comm		= "watchdog/%u",
-	.setup			= watchdog_enable,
-	.park			= watchdog_disable,
-	.unpark			= watchdog_enable,
-};
-
 void __init lockup_detector_init(void)
 {
 	set_sample_period();
-	if (smpboot_register_percpu_thread(&watchdog_threads)) {
-		pr_err("Failed to create watchdog threads, disabled\n");
-		watchdog_disabled = -ENODEV;
-	}
+
+	if (watchdog_enabled)
+		watchdog_enable_all_cpus();
 }