watchdog: Add support for cpu isolation

Open up interface to allow external subsystem to enable and disable hard
lockup detector.

Change-Id: I88a728ee1d54aaa887fab52e5e40d1d4e4fc69ca
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>

4 files changed, 34 insertions, 2 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index b7d56c5ea3c6..3ac683dff7de 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -72,6 +72,11 @@ int lock_device_hotplug_sysfs(void)
 	return restart_syscall();
 }
 
+void lock_device_hotplug_assert(void)
+{
+	lockdep_assert_held(&device_hotplug_lock);
+}
+
 #ifdef CONFIG_BLOCK
 static inline int device_is_not_partition(struct device *dev)
 {
diff --git a/include/linux/device.h b/include/linux/device.h
index 9f27351c6b9c..4b4e2d5ce6e7 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1023,6 +1023,7 @@ static inline bool device_supports_offline(struct device *dev)
 extern void lock_device_hotplug(void);
 extern void unlock_device_hotplug(void);
 extern int lock_device_hotplug_sysfs(void);
+extern void lock_device_hotplug_assert(void);
 extern int device_offline(struct device *dev);
 extern int device_online(struct device *dev);
 extern void set_primary_fwnode(struct device *dev, struct fwnode_handle *fwnode);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 4701e0403167..ac6b519494a2 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -409,6 +409,8 @@ extern int proc_dowatchdog_thresh(struct ctl_table *table, int write,
 extern unsigned int  softlockup_panic;
 extern unsigned int  hardlockup_panic;
 void lockup_detector_init(void);
+extern void watchdog_enable(unsigned int cpu);
+extern void watchdog_disable(unsigned int cpu);
 #else
 static inline void touch_softlockup_watchdog_sched(void)
 {
@@ -425,6 +427,12 @@ static inline void touch_all_softlockup_watchdogs(void)
 static inline void lockup_detector_init(void)
 {
 }
+static inline void watchdog_enable(unsigned int cpu)
+{
+}
+static inline void watchdog_disable(unsigned int cpu)
+{
+}
 #endif
 
 #ifdef CONFIG_DETECT_HUNG_TASK
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 029da92fb712..7f21591c8ec5 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -13,6 +13,7 @@
 
 #include <linux/mm.h>
 #include <linux/cpu.h>
+#include <linux/device.h>
 #include <linux/nmi.h>
 #include <linux/init.h>
 #include <linux/module.h>
@@ -95,6 +96,7 @@ static u64 __read_mostly sample_period;
 static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts);
 static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog);
 static DEFINE_PER_CPU(struct hrtimer, watchdog_hrtimer);
+static DEFINE_PER_CPU(unsigned int, watchdog_en);
 static DEFINE_PER_CPU(bool, softlockup_touch_sync);
 static DEFINE_PER_CPU(bool, soft_watchdog_warn);
 static DEFINE_PER_CPU(unsigned long, hrtimer_interrupts);
@@ -586,9 +588,17 @@ static void watchdog_set_prio(unsigned int policy, unsigned int prio)
 	sched_setscheduler(current, policy, &param);
 }
 
-static void watchdog_enable(unsigned int cpu)
+/* Must be called with hotplug lock (lock_device_hotplug()) held. */
+void watchdog_enable(unsigned int cpu)
 {
 	struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
+	unsigned int *enabled = raw_cpu_ptr(&watchdog_en);
+
+	lock_device_hotplug_assert();
+
+	if (*enabled)
+		return;
+	*enabled = 1;
 
 	/* kick off the timer for the hardlockup detector */
 	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
@@ -606,9 +616,17 @@ static void watchdog_enable(unsigned int cpu)
 	__touch_watchdog();
 }
 
-static void watchdog_disable(unsigned int cpu)
+/* Must be called with hotplug lock (lock_device_hotplug()) held. */
+void watchdog_disable(unsigned int cpu)
 {
 	struct hrtimer *hrtimer = raw_cpu_ptr(&watchdog_hrtimer);
+	unsigned int *enabled = raw_cpu_ptr(&watchdog_en);
+
+	lock_device_hotplug_assert();
+
+	if (!*enabled)
+		return;
+	*enabled = 0;
 
 	watchdog_set_prio(SCHED_NORMAL, 0);
 	hrtimer_cancel(hrtimer);