sched: Simplify cpu-hot-unplug task migration (48c5ccae) · Commits · e / devices / android_kernel_teracube_2e

include/linux/sched.h

+0 −3

Original line number	Diff line number	Diff line
		@@ -1871,14 +1871,11 @@ extern void sched_clock_idle_sleep_event(void);
		extern void sched_clock_idle_wakeup_event(u64 delta_ns);

		#ifdef CONFIG_HOTPLUG_CPU
		extern void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p);
		extern void idle_task_exit(void);
		#else
		static inline void idle_task_exit(void) {}
		#endif

		extern void sched_idle_next(void);

		#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
		extern void wake_up_idle_cpu(int cpu);
		#else

kernel/cpu.c

+6 −10

Original line number	Diff line number	Diff line
		@@ -189,7 +189,6 @@ static inline void check_for_tasks(int cpu)
		}

		struct take_cpu_down_param {
		struct task_struct *caller;
		unsigned long mod;
		void *hcpu;
		};
		@@ -208,11 +207,6 @@ static int __ref take_cpu_down(void *_param)

		cpu_notify(CPU_DYING \| param->mod, param->hcpu);

		if (task_cpu(param->caller) == cpu)
		move_task_off_dead_cpu(cpu, param->caller);
		/* Force idle task to run as soon as we yield: it should
		immediately notice cpu is offline and die quickly. */
		sched_idle_next();
		return 0;
		}

		@@ -223,7 +217,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
		void hcpu = (void )(long)cpu;
		unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
		struct take_cpu_down_param tcd_param = {
		.caller = current,
		.mod = mod,
		.hcpu = hcpu,
		};
		@@ -253,9 +246,12 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
		}
		BUG_ON(cpu_online(cpu));

		/* Wait for it to sleep (leaving idle task). */
		while (!idle_cpu(cpu))
		yield();
		/*
		* The migration_call() CPU_DYING callback will have removed all
		* runnable tasks from the cpu, there's only the idle task left now
		* that the migration thread is done doing the stop_machine thing.
		*/
		BUG_ON(!idle_cpu(cpu));

		/* This actually kills the CPU. */
		__cpu_die(cpu);

kernel/sched.c

+61 −145

Original line number	Diff line number	Diff line
		@@ -2366,7 +2366,6 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
		return dest_cpu;

		/* No more Mr. Nice Guy. */
		if (unlikely(dest_cpu >= nr_cpu_ids)) {
		dest_cpu = cpuset_cpus_allowed_fallback(p);
		/*
		* Don't tell them about moving exiting tasks or
		@@ -2374,11 +2373,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
		* leave kernel.
		*/
		if (p->mm && printk_ratelimit()) {
		printk(KERN_INFO "process %d (%s) no "
		"longer affine to cpu%d\n",
		printk(KERN_INFO "process %d (%s) no longer affine to cpu%d\n",
		task_pid_nr(p), p->comm, cpu);
		}
		}

		return dest_cpu;
		}
		@@ -5712,29 +5709,20 @@ static int migration_cpu_stop(void *data)
		}

		#ifdef CONFIG_HOTPLUG_CPU

		/*
		* Figure out where task on dead CPU should go, use force if necessary.
		* Ensures that the idle task is using init_mm right before its cpu goes
		* offline.
		*/
		void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
		void idle_task_exit(void)
		{
		struct rq *rq = cpu_rq(dead_cpu);
		int needs_cpu, uninitialized_var(dest_cpu);
		unsigned long flags;
		struct mm_struct *mm = current->active_mm;

		local_irq_save(flags);
		BUG_ON(cpu_online(smp_processor_id()));

		raw_spin_lock(&rq->lock);
		needs_cpu = (task_cpu(p) == dead_cpu) && (p->state != TASK_WAKING);
		if (needs_cpu)
		dest_cpu = select_fallback_rq(dead_cpu, p);
		raw_spin_unlock(&rq->lock);
		/*
		* It can only fail if we race with set_cpus_allowed(),
		* in the racer should migrate the task anyway.
		*/
		if (needs_cpu)
		__migrate_task(p, dead_cpu, dest_cpu);
		local_irq_restore(flags);
		if (mm != &init_mm)
		switch_mm(mm, &init_mm, current);
		mmdrop(mm);
		}

		/*
		@@ -5747,128 +5735,69 @@ void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
		static void migrate_nr_uninterruptible(struct rq *rq_src)
		{
		struct rq *rq_dest = cpu_rq(cpumask_any(cpu_active_mask));
		unsigned long flags;

		local_irq_save(flags);
		double_rq_lock(rq_src, rq_dest);
		rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible;
		rq_src->nr_uninterruptible = 0;
		double_rq_unlock(rq_src, rq_dest);
		local_irq_restore(flags);
		}

		/* Run through task list and migrate tasks from the dead cpu. */
		static void migrate_live_tasks(int src_cpu)
		{
		struct task_struct p, t;

		read_lock(&tasklist_lock);

		do_each_thread(t, p) {
		if (p == current)
		continue;

		if (task_cpu(p) == src_cpu)
		move_task_off_dead_cpu(src_cpu, p);
		} while_each_thread(t, p);

		read_unlock(&tasklist_lock);
		}

		/*
		* Schedules idle task to be the next runnable task on current CPU.
		* It does so by boosting its priority to highest possible.
		* Used by CPU offline code.
		* remove the tasks which were accounted by rq from calc_load_tasks.
		*/
		void sched_idle_next(void)
		static void calc_global_load_remove(struct rq *rq)
		{
		int this_cpu = smp_processor_id();
		struct rq *rq = cpu_rq(this_cpu);
		struct task_struct *p = rq->idle;
		unsigned long flags;

		/* cpu has to be offline */
		BUG_ON(cpu_online(this_cpu));

		/*
		* Strictly not necessary since rest of the CPUs are stopped by now
		* and interrupts disabled on the current cpu.
		*/
		raw_spin_lock_irqsave(&rq->lock, flags);

		__setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);

		activate_task(rq, p, 0);

		raw_spin_unlock_irqrestore(&rq->lock, flags);
		atomic_long_sub(rq->calc_load_active, &calc_load_tasks);
		rq->calc_load_active = 0;
		}

		/*
		* Ensures that the idle task is using init_mm right before its cpu goes
		* offline.
		* Migrate all tasks from the rq, sleeping tasks will be migrated by
		* try_to_wake_up()->select_task_rq().
		*
		* Called with rq->lock held even though we'er in stop_machine() and
		* there's no concurrency possible, we hold the required locks anyway
		* because of lock validation efforts.
		*/
		void idle_task_exit(void)
		{
		struct mm_struct *mm = current->active_mm;

		BUG_ON(cpu_online(smp_processor_id()));

		if (mm != &init_mm)
		switch_mm(mm, &init_mm, current);
		mmdrop(mm);
		}

		/* called under rq->lock with disabled interrupts */
		static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
		static void migrate_tasks(unsigned int dead_cpu)
		{
		struct rq *rq = cpu_rq(dead_cpu);

		/* Must be exiting, otherwise would be on tasklist. */
		BUG_ON(!p->exit_state);

		/* Cannot have done final schedule yet: would have vanished. */
		BUG_ON(p->state == TASK_DEAD);

		get_task_struct(p);
		struct task_struct next, stop = rq->stop;
		int dest_cpu;

		/*
		* Drop lock around migration; if someone else moves it,
		* that's OK. No task can be added to this CPU, so iteration is
		* fine.
		* Fudge the rq selection such that the below task selection loop
		* doesn't get stuck on the currently eligible stop task.
		*
		* We're currently inside stop_machine() and the rq is either stuck
		* in the stop_machine_cpu_stop() loop, or we're executing this code,
		* either way we should never end up calling schedule() until we're
		* done here.
		*/
		raw_spin_unlock_irq(&rq->lock);
		move_task_off_dead_cpu(dead_cpu, p);
		raw_spin_lock_irq(&rq->lock);

		put_task_struct(p);
		}

		/* release_task() removes task from tasklist, so we won't find dead tasks. */
		static void migrate_dead_tasks(unsigned int dead_cpu)
		{
		struct rq *rq = cpu_rq(dead_cpu);
		struct task_struct *next;
		rq->stop = NULL;

		for ( ; ; ) {
		if (!rq->nr_running)
		/*
		* There's this thread running, bail when that's the only
		* remaining thread.
		*/
		if (rq->nr_running == 1)
		break;

		next = pick_next_task(rq);
		if (!next)
		break;
		BUG_ON(!next);
		next->sched_class->put_prev_task(rq, next);
		migrate_dead(dead_cpu, next);

		}
		/* Find suitable destination for @next, with force if needed. */
		dest_cpu = select_fallback_rq(dead_cpu, next);
		raw_spin_unlock(&rq->lock);

		__migrate_task(next, dead_cpu, dest_cpu);

		raw_spin_lock(&rq->lock);
		}

		/*
		* remove the tasks which were accounted by rq from calc_load_tasks.
		*/
		static void calc_global_load_remove(struct rq *rq)
		{
		atomic_long_sub(rq->calc_load_active, &calc_load_tasks);
		rq->calc_load_active = 0;
		rq->stop = stop;
		}

		#endif /* CONFIG_HOTPLUG_CPU */

		#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL)
		@@ -6078,15 +6007,13 @@ migration_call(struct notifier_block nfb, unsigned long action, void hcpu)
		unsigned long flags;
		struct rq *rq = cpu_rq(cpu);

		switch (action) {
		switch (action & ~CPU_TASKS_FROZEN) {

		case CPU_UP_PREPARE:
		case CPU_UP_PREPARE_FROZEN:
		rq->calc_load_update = calc_load_update;
		break;

		case CPU_ONLINE:
		case CPU_ONLINE_FROZEN:
		/* Update our root-domain */
		raw_spin_lock_irqsave(&rq->lock, flags);
		if (rq->rd) {
		@@ -6098,30 +6025,19 @@ migration_call(struct notifier_block nfb, unsigned long action, void hcpu)
		break;

		#ifdef CONFIG_HOTPLUG_CPU
		case CPU_DEAD:
		case CPU_DEAD_FROZEN:
		migrate_live_tasks(cpu);
		/* Idle task back to normal (off runqueue, low prio) */
		raw_spin_lock_irq(&rq->lock);
		deactivate_task(rq, rq->idle, 0);
		__setscheduler(rq, rq->idle, SCHED_NORMAL, 0);
		rq->idle->sched_class = &idle_sched_class;
		migrate_dead_tasks(cpu);
		raw_spin_unlock_irq(&rq->lock);
		migrate_nr_uninterruptible(rq);
		BUG_ON(rq->nr_running != 0);
		calc_global_load_remove(rq);
		break;

		case CPU_DYING:
		case CPU_DYING_FROZEN:
		/* Update our root-domain */
		raw_spin_lock_irqsave(&rq->lock, flags);
		if (rq->rd) {
		BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
		set_rq_offline(rq);
		}
		migrate_tasks(cpu);
		BUG_ON(rq->nr_running != 1); /* the migration thread */
		raw_spin_unlock_irqrestore(&rq->lock, flags);

		migrate_nr_uninterruptible(rq);
		calc_global_load_remove(rq);
		break;
		#endif
		}