Merge "sched: Ensure watchdog is enabled before disabling" (a97a6be4) · Commits · e / devices / android_kernel_sony_msm8998

include/linux/sched.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -446,6 +446,7 @@ extern unsigned int hardlockup_panic;
		void lockup_detector_init(void);
		extern void watchdog_enable(unsigned int cpu);
		extern void watchdog_disable(unsigned int cpu);
		extern bool watchdog_configured(unsigned int cpu);
		#else
		static inline void touch_softlockup_watchdog_sched(void)
		{
		@@ -468,6 +469,14 @@ static inline void watchdog_enable(unsigned int cpu)
		static inline void watchdog_disable(unsigned int cpu)
		{
		}
		static inline bool watchdog_configured(unsigned int cpu)
		{
		/*
		* Predend the watchdog is always configured.
		* We will be waiting for the watchdog to be enabled in core isolation
		*/
		return true;
		}
		#endif

		#ifdef CONFIG_DETECT_HUNG_TASK

kernel/sched/core.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -5696,6 +5696,22 @@ int sched_isolate_cpu(int cpu)
		if (++cpu_isolation_vote[cpu] > 1)
		goto out;

		/*
		* There is a race between watchdog being enabled by hotplug and
		* core isolation disabling the watchdog. When a CPU is hotplugged in
		* and the hotplug lock has been released the watchdog thread might
		* not have run yet to enable the watchdog.
		* We have to wait for the watchdog to be enabled before proceeding.
		*/
		if (!watchdog_configured(cpu)) {
		msleep(20);
		if (!watchdog_configured(cpu)) {
		--cpu_isolation_vote[cpu];
		ret_code = -EBUSY;
		goto out;
		}
		}

		set_cpu_isolated(cpu, true);
		cpumask_clear_cpu(cpu, &avail_cpus);

kernel/watchdog.c

+20 −8

Original line number	Diff line number	Diff line
		@@ -588,17 +588,13 @@ static void watchdog_set_prio(unsigned int policy, unsigned int prio)
		sched_setscheduler(current, policy, &param);
		}

		/* 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);
		@@ -614,24 +610,40 @@ void watchdog_enable(unsigned int cpu)
		/* initialize timestamp */
		watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);
		__touch_watchdog();

		/*
		* Need to ensure above operations are observed by other CPUs before
		* indicating that timer is enabled. This is to synchronize core
		* isolation and hotplug. Core isolation will wait for this flag to be
		* set.
		*/
		mb();
		*enabled = 1;
		}

		/* 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);
		/* disable the perf event */
		watchdog_nmi_disable(cpu);

		/*
		* No need for barrier here since disabling the watchdog is
		* synchronized with hotplug lock
		*/
		*enabled = 0;
		}

		bool watchdog_configured(unsigned int cpu)
		{
		return *per_cpu_ptr(&watchdog_en, cpu);
		}

		static void watchdog_cleanup(unsigned int cpu, bool online)