| /* |
| * Common SMP CPU bringup/teardown functions |
| */ |
| #include <linux/cpu.h> |
| #include <linux/err.h> |
| #include <linux/smp.h> |
| #include <linux/delay.h> |
| #include <linux/init.h> |
| #include <linux/list.h> |
| #include <linux/slab.h> |
| #include <linux/sched.h> |
| #include <linux/export.h> |
| #include <linux/percpu.h> |
| #include <linux/kthread.h> |
| #include <linux/smpboot.h> |
| |
| #include "smpboot.h" |
| |
| #ifdef CONFIG_SMP |
| |
| #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD |
| /* |
| * For the hotplug case we keep the task structs around and reuse |
| * them. |
| */ |
| static DEFINE_PER_CPU(struct task_struct *, idle_threads); |
| |
| struct task_struct *idle_thread_get(unsigned int cpu) |
| { |
| struct task_struct *tsk = per_cpu(idle_threads, cpu); |
| |
| if (!tsk) |
| return ERR_PTR(-ENOMEM); |
| init_idle(tsk, cpu); |
| return tsk; |
| } |
| |
| void __init idle_thread_set_boot_cpu(void) |
| { |
| per_cpu(idle_threads, smp_processor_id()) = current; |
| } |
| |
| /** |
| * idle_init - Initialize the idle thread for a cpu |
| * @cpu: The cpu for which the idle thread should be initialized |
| * |
| * Creates the thread if it does not exist. |
| */ |
| static inline void idle_init(unsigned int cpu) |
| { |
| struct task_struct *tsk = per_cpu(idle_threads, cpu); |
| |
| if (!tsk) { |
| tsk = fork_idle(cpu); |
| if (IS_ERR(tsk)) |
| pr_err("SMP: fork_idle() failed for CPU %u\n", cpu); |
| else |
| per_cpu(idle_threads, cpu) = tsk; |
| } |
| } |
| |
| /** |
| * idle_threads_init - Initialize idle threads for all cpus |
| */ |
| void __init idle_threads_init(void) |
| { |
| unsigned int cpu, boot_cpu; |
| |
| boot_cpu = smp_processor_id(); |
| |
| for_each_possible_cpu(cpu) { |
| if (cpu != boot_cpu) |
| idle_init(cpu); |
| } |
| } |
| #endif |
| |
| #endif /* #ifdef CONFIG_SMP */ |
| |
| static LIST_HEAD(hotplug_threads); |
| static DEFINE_MUTEX(smpboot_threads_lock); |
| |
| struct smpboot_thread_data { |
| unsigned int cpu; |
| unsigned int status; |
| struct smp_hotplug_thread *ht; |
| }; |
| |
| enum { |
| HP_THREAD_NONE = 0, |
| HP_THREAD_ACTIVE, |
| HP_THREAD_PARKED, |
| }; |
| |
| /** |
| * smpboot_thread_fn - percpu hotplug thread loop function |
| * @data: thread data pointer |
| * |
| * Checks for thread stop and park conditions. Calls the necessary |
| * setup, cleanup, park and unpark functions for the registered |
| * thread. |
| * |
| * Returns 1 when the thread should exit, 0 otherwise. |
| */ |
| static int smpboot_thread_fn(void *data) |
| { |
| struct smpboot_thread_data *td = data; |
| struct smp_hotplug_thread *ht = td->ht; |
| |
| while (1) { |
| set_current_state(TASK_INTERRUPTIBLE); |
| preempt_disable(); |
| if (kthread_should_stop()) { |
| __set_current_state(TASK_RUNNING); |
| preempt_enable(); |
| if (ht->cleanup) |
| ht->cleanup(td->cpu, cpu_online(td->cpu)); |
| kfree(td); |
| return 0; |
| } |
| |
| if (kthread_should_park()) { |
| __set_current_state(TASK_RUNNING); |
| preempt_enable(); |
| if (ht->park && td->status == HP_THREAD_ACTIVE) { |
| BUG_ON(td->cpu != smp_processor_id()); |
| ht->park(td->cpu); |
| td->status = HP_THREAD_PARKED; |
| } |
| kthread_parkme(); |
| /* We might have been woken for stop */ |
| continue; |
| } |
| |
| BUG_ON(td->cpu != smp_processor_id()); |
| |
| /* Check for state change setup */ |
| switch (td->status) { |
| case HP_THREAD_NONE: |
| __set_current_state(TASK_RUNNING); |
| preempt_enable(); |
| if (ht->setup) |
| ht->setup(td->cpu); |
| td->status = HP_THREAD_ACTIVE; |
| continue; |
| |
| case HP_THREAD_PARKED: |
| __set_current_state(TASK_RUNNING); |
| preempt_enable(); |
| if (ht->unpark) |
| ht->unpark(td->cpu); |
| td->status = HP_THREAD_ACTIVE; |
| continue; |
| } |
| |
| if (!ht->thread_should_run(td->cpu)) { |
| preempt_enable_no_resched(); |
| schedule(); |
| } else { |
| __set_current_state(TASK_RUNNING); |
| preempt_enable(); |
| ht->thread_fn(td->cpu); |
| } |
| } |
| } |
| |
| static int |
| __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu) |
| { |
| struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu); |
| struct smpboot_thread_data *td; |
| |
| if (tsk) |
| return 0; |
| |
| td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu)); |
| if (!td) |
| return -ENOMEM; |
| td->cpu = cpu; |
| td->ht = ht; |
| |
| tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu, |
| ht->thread_comm); |
| if (IS_ERR(tsk)) { |
| kfree(td); |
| return PTR_ERR(tsk); |
| } |
| get_task_struct(tsk); |
| *per_cpu_ptr(ht->store, cpu) = tsk; |
| if (ht->create) { |
| /* |
| * Make sure that the task has actually scheduled out |
| * into park position, before calling the create |
| * callback. At least the migration thread callback |
| * requires that the task is off the runqueue. |
| */ |
| if (!wait_task_inactive(tsk, TASK_PARKED)) |
| WARN_ON(1); |
| else |
| ht->create(cpu); |
| } |
| return 0; |
| } |
| |
| int smpboot_create_threads(unsigned int cpu) |
| { |
| struct smp_hotplug_thread *cur; |
| int ret = 0; |
| |
| mutex_lock(&smpboot_threads_lock); |
| list_for_each_entry(cur, &hotplug_threads, list) { |
| ret = __smpboot_create_thread(cur, cpu); |
| if (ret) |
| break; |
| } |
| mutex_unlock(&smpboot_threads_lock); |
| return ret; |
| } |
| |
| static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu) |
| { |
| struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu); |
| |
| if (ht->pre_unpark) |
| ht->pre_unpark(cpu); |
| kthread_unpark(tsk); |
| } |
| |
| void smpboot_unpark_threads(unsigned int cpu) |
| { |
| struct smp_hotplug_thread *cur; |
| |
| mutex_lock(&smpboot_threads_lock); |
| list_for_each_entry(cur, &hotplug_threads, list) |
| smpboot_unpark_thread(cur, cpu); |
| mutex_unlock(&smpboot_threads_lock); |
| } |
| |
| static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu) |
| { |
| struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu); |
| |
| if (tsk && !ht->selfparking) |
| kthread_park(tsk); |
| } |
| |
| void smpboot_park_threads(unsigned int cpu) |
| { |
| struct smp_hotplug_thread *cur; |
| |
| mutex_lock(&smpboot_threads_lock); |
| list_for_each_entry_reverse(cur, &hotplug_threads, list) |
| smpboot_park_thread(cur, cpu); |
| mutex_unlock(&smpboot_threads_lock); |
| } |
| |
| static void smpboot_destroy_threads(struct smp_hotplug_thread *ht) |
| { |
| unsigned int cpu; |
| |
| /* We need to destroy also the parked threads of offline cpus */ |
| for_each_possible_cpu(cpu) { |
| struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu); |
| |
| if (tsk) { |
| kthread_stop(tsk); |
| put_task_struct(tsk); |
| *per_cpu_ptr(ht->store, cpu) = NULL; |
| } |
| } |
| } |
| |
| /** |
| * smpboot_register_percpu_thread - Register a per_cpu thread related to hotplug |
| * @plug_thread: Hotplug thread descriptor |
| * |
| * Creates and starts the threads on all online cpus. |
| */ |
| int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread) |
| { |
| unsigned int cpu; |
| int ret = 0; |
| |
| get_online_cpus(); |
| mutex_lock(&smpboot_threads_lock); |
| for_each_online_cpu(cpu) { |
| ret = __smpboot_create_thread(plug_thread, cpu); |
| if (ret) { |
| smpboot_destroy_threads(plug_thread); |
| goto out; |
| } |
| smpboot_unpark_thread(plug_thread, cpu); |
| } |
| list_add(&plug_thread->list, &hotplug_threads); |
| out: |
| mutex_unlock(&smpboot_threads_lock); |
| put_online_cpus(); |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread); |
| |
| /** |
| * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug |
| * @plug_thread: Hotplug thread descriptor |
| * |
| * Stops all threads on all possible cpus. |
| */ |
| void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread) |
| { |
| get_online_cpus(); |
| mutex_lock(&smpboot_threads_lock); |
| list_del(&plug_thread->list); |
| smpboot_destroy_threads(plug_thread); |
| mutex_unlock(&smpboot_threads_lock); |
| put_online_cpus(); |
| } |
| EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread); |
| |
| static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD); |
| |
| /* |
| * Called to poll specified CPU's state, for example, when waiting for |
| * a CPU to come online. |
| */ |
| int cpu_report_state(int cpu) |
| { |
| return atomic_read(&per_cpu(cpu_hotplug_state, cpu)); |
| } |
| |
| /* |
| * If CPU has died properly, set its state to CPU_UP_PREPARE and |
| * return success. Otherwise, return -EBUSY if the CPU died after |
| * cpu_wait_death() timed out. And yet otherwise again, return -EAGAIN |
| * if cpu_wait_death() timed out and the CPU still hasn't gotten around |
| * to dying. In the latter two cases, the CPU might not be set up |
| * properly, but it is up to the arch-specific code to decide. |
| * Finally, -EIO indicates an unanticipated problem. |
| * |
| * Note that it is permissible to omit this call entirely, as is |
| * done in architectures that do no CPU-hotplug error checking. |
| */ |
| int cpu_check_up_prepare(int cpu) |
| { |
| if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) { |
| atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE); |
| return 0; |
| } |
| |
| switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) { |
| |
| case CPU_POST_DEAD: |
| |
| /* The CPU died properly, so just start it up again. */ |
| atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE); |
| return 0; |
| |
| case CPU_DEAD_FROZEN: |
| |
| /* |
| * Timeout during CPU death, so let caller know. |
| * The outgoing CPU completed its processing, but after |
| * cpu_wait_death() timed out and reported the error. The |
| * caller is free to proceed, in which case the state |
| * will be reset properly by cpu_set_state_online(). |
| * Proceeding despite this -EBUSY return makes sense |
| * for systems where the outgoing CPUs take themselves |
| * offline, with no post-death manipulation required from |
| * a surviving CPU. |
| */ |
| return -EBUSY; |
| |
| case CPU_BROKEN: |
| |
| /* |
| * The most likely reason we got here is that there was |
| * a timeout during CPU death, and the outgoing CPU never |
| * did complete its processing. This could happen on |
| * a virtualized system if the outgoing VCPU gets preempted |
| * for more than five seconds, and the user attempts to |
| * immediately online that same CPU. Trying again later |
| * might return -EBUSY above, hence -EAGAIN. |
| */ |
| return -EAGAIN; |
| |
| default: |
| |
| /* Should not happen. Famous last words. */ |
| return -EIO; |
| } |
| } |
| |
| /* |
| * Mark the specified CPU online. |
| * |
| * Note that it is permissible to omit this call entirely, as is |
| * done in architectures that do no CPU-hotplug error checking. |
| */ |
| void cpu_set_state_online(int cpu) |
| { |
| (void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE); |
| } |
| |
| #ifdef CONFIG_HOTPLUG_CPU |
| |
| /* |
| * Wait for the specified CPU to exit the idle loop and die. |
| */ |
| bool cpu_wait_death(unsigned int cpu, int seconds) |
| { |
| int jf_left = seconds * HZ; |
| int oldstate; |
| bool ret = true; |
| int sleep_jf = 1; |
| |
| might_sleep(); |
| |
| /* The outgoing CPU will normally get done quite quickly. */ |
| if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD) |
| goto update_state; |
| udelay(5); |
| |
| /* But if the outgoing CPU dawdles, wait increasingly long times. */ |
| while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) { |
| schedule_timeout_uninterruptible(sleep_jf); |
| jf_left -= sleep_jf; |
| if (jf_left <= 0) |
| break; |
| sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10); |
| } |
| update_state: |
| oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu)); |
| if (oldstate == CPU_DEAD) { |
| /* Outgoing CPU died normally, update state. */ |
| smp_mb(); /* atomic_read() before update. */ |
| atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD); |
| } else { |
| /* Outgoing CPU still hasn't died, set state accordingly. */ |
| if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu), |
| oldstate, CPU_BROKEN) != oldstate) |
| goto update_state; |
| ret = false; |
| } |
| return ret; |
| } |
| |
| /* |
| * Called by the outgoing CPU to report its successful death. Return |
| * false if this report follows the surviving CPU's timing out. |
| * |
| * A separate "CPU_DEAD_FROZEN" is used when the surviving CPU |
| * timed out. This approach allows architectures to omit calls to |
| * cpu_check_up_prepare() and cpu_set_state_online() without defeating |
| * the next cpu_wait_death()'s polling loop. |
| */ |
| bool cpu_report_death(void) |
| { |
| int oldstate; |
| int newstate; |
| int cpu = smp_processor_id(); |
| |
| do { |
| oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu)); |
| if (oldstate != CPU_BROKEN) |
| newstate = CPU_DEAD; |
| else |
| newstate = CPU_DEAD_FROZEN; |
| } while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu), |
| oldstate, newstate) != oldstate); |
| return newstate == CPU_DEAD; |
| } |
| |
| #endif /* #ifdef CONFIG_HOTPLUG_CPU */ |