From b4b7ff4b08e691656c9d77c758fc355833128ac0 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Andr=C3=A9=20Fabian=20Silva=20Delgado?= Date: Wed, 20 Jan 2016 14:01:31 -0300 Subject: Linux-libre 4.4-gnu --- kernel/stop_machine.c | 94 ++++++++++++++++++++++++++++++--------------------- 1 file changed, 56 insertions(+), 38 deletions(-) (limited to 'kernel/stop_machine.c') diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 12484e5d5..a3bbaee77 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -73,21 +73,24 @@ static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed) } } +static void __cpu_stop_queue_work(struct cpu_stopper *stopper, + struct cpu_stop_work *work) +{ + list_add_tail(&work->list, &stopper->works); + wake_up_process(stopper->thread); +} + /* queue @work to @stopper. if offline, @work is completed immediately */ static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work) { struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); - unsigned long flags; spin_lock_irqsave(&stopper->lock, flags); - - if (stopper->enabled) { - list_add_tail(&work->list, &stopper->works); - wake_up_process(stopper->thread); - } else + if (stopper->enabled) + __cpu_stop_queue_work(stopper, work); + else cpu_stop_signal_done(work->done, false); - spin_unlock_irqrestore(&stopper->lock, flags); } @@ -213,6 +216,31 @@ static int multi_cpu_stop(void *data) return err; } +static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1, + int cpu2, struct cpu_stop_work *work2) +{ + struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1); + struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2); + int err; + + lg_double_lock(&stop_cpus_lock, cpu1, cpu2); + spin_lock_irq(&stopper1->lock); + spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING); + + err = -ENOENT; + if (!stopper1->enabled || !stopper2->enabled) + goto unlock; + + err = 0; + __cpu_stop_queue_work(stopper1, work1); + __cpu_stop_queue_work(stopper2, work2); +unlock: + spin_unlock(&stopper2->lock); + spin_unlock_irq(&stopper1->lock); + lg_double_unlock(&stop_cpus_lock, cpu1, cpu2); + + return err; +} /** * stop_two_cpus - stops two cpus * @cpu1: the cpu to stop @@ -247,24 +275,13 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void * cpu_stop_init_done(&done, 2); set_state(&msdata, MULTI_STOP_PREPARE); - /* - * If we observe both CPUs active we know _cpu_down() cannot yet have - * queued its stop_machine works and therefore ours will get executed - * first. Or its not either one of our CPUs that's getting unplugged, - * in which case we don't care. - * - * This relies on the stopper workqueues to be FIFO. - */ - if (!cpu_active(cpu1) || !cpu_active(cpu2)) { + if (cpu1 > cpu2) + swap(cpu1, cpu2); + if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2)) { preempt_enable(); return -ENOENT; } - lg_double_lock(&stop_cpus_lock, cpu1, cpu2); - cpu_stop_queue_work(cpu1, &work1); - cpu_stop_queue_work(cpu2, &work2); - lg_double_unlock(&stop_cpus_lock, cpu1, cpu2); - preempt_enable(); wait_for_completion(&done.completion); @@ -452,6 +469,18 @@ repeat: } } +void stop_machine_park(int cpu) +{ + struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); + /* + * Lockless. cpu_stopper_thread() will take stopper->lock and flush + * the pending works before it parks, until then it is fine to queue + * the new works. + */ + stopper->enabled = false; + kthread_park(stopper->thread); +} + extern void sched_set_stop_task(int cpu, struct task_struct *stop); static void cpu_stop_create(unsigned int cpu) @@ -462,26 +491,16 @@ static void cpu_stop_create(unsigned int cpu) static void cpu_stop_park(unsigned int cpu) { struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); - struct cpu_stop_work *work, *tmp; - unsigned long flags; - /* drain remaining works */ - spin_lock_irqsave(&stopper->lock, flags); - list_for_each_entry_safe(work, tmp, &stopper->works, list) { - list_del_init(&work->list); - cpu_stop_signal_done(work->done, false); - } - stopper->enabled = false; - spin_unlock_irqrestore(&stopper->lock, flags); + WARN_ON(!list_empty(&stopper->works)); } -static void cpu_stop_unpark(unsigned int cpu) +void stop_machine_unpark(int cpu) { struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu); - spin_lock_irq(&stopper->lock); stopper->enabled = true; - spin_unlock_irq(&stopper->lock); + kthread_unpark(stopper->thread); } static struct smp_hotplug_thread cpu_stop_threads = { @@ -490,9 +509,7 @@ static struct smp_hotplug_thread cpu_stop_threads = { .thread_fn = cpu_stopper_thread, .thread_comm = "migration/%u", .create = cpu_stop_create, - .setup = cpu_stop_unpark, .park = cpu_stop_park, - .pre_unpark = cpu_stop_unpark, .selfparking = true, }; @@ -508,12 +525,13 @@ static int __init cpu_stop_init(void) } BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads)); + stop_machine_unpark(raw_smp_processor_id()); stop_machine_initialized = true; return 0; } early_initcall(cpu_stop_init); -#ifdef CONFIG_STOP_MACHINE +#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU) static int __stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus) { @@ -613,4 +631,4 @@ int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data, return ret ?: done.ret; } -#endif /* CONFIG_STOP_MACHINE */ +#endif /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */ -- cgit v1.2.3