Merge "sched: Ensure watchdog is enabled before disabling" (527706a7) · Commits · e / devices / android_kernel_xiaomi_nabu

kernel/sched/core.c

+17 −0

Original line number	Diff line number	Diff line
		@@ -27,6 +27,7 @@
		#include <linux/security.h>
		#include <linux/syscalls.h>
		#include <linux/irq.h>
		#include <linux/delay.h>

		#include <linux/kthread.h>

		@@ -5985,6 +5986,22 @@ 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
		@@ -456,17 +456,13 @@ 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 = this_cpu_ptr(&watchdog_hrtimer);
		unsigned int *enabled = this_cpu_ptr(&watchdog_en);

		lock_device_hotplug_assert();

		if (*enabled)
		return;
		*enabled = 1;

		/*
		* Start the timer first to prevent the NMI watchdog triggering
		@@ -484,19 +480,24 @@ void watchdog_enable(unsigned int cpu)
		watchdog_nmi_enable(cpu);

		watchdog_set_prio(SCHED_FIFO, MAX_RT_PRIO - 1);

		/*
		* 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 = this_cpu_ptr(&watchdog_hrtimer);
		unsigned int *enabled = this_cpu_ptr(&watchdog_en);

		lock_device_hotplug_assert();

		if (!*enabled)
		return;
		*enabled = 0;

		watchdog_set_prio(SCHED_NORMAL, 0);
		/*
		@@ -506,6 +507,17 @@ void watchdog_disable(unsigned int cpu)
		*/
		watchdog_nmi_disable(cpu);
		hrtimer_cancel(hrtimer);

		/*
		* 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)