315 lines
6.9 KiB
C
315 lines
6.9 KiB
C
/*
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* Common SMP CPU bringup/teardown functions
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*/
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#include <linux/cpu.h>
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#include <linux/err.h>
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#include <linux/smp.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/export.h>
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#include <linux/percpu.h>
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#include <linux/kthread.h>
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#include <linux/smpboot.h>
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#include "smpboot.h"
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#ifdef CONFIG_SMP
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#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
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/*
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* For the hotplug case we keep the task structs around and reuse
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* them.
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*/
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static DEFINE_PER_CPU(struct task_struct *, idle_threads);
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struct task_struct *idle_thread_get(unsigned int cpu)
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{
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struct task_struct *tsk = per_cpu(idle_threads, cpu);
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if (!tsk)
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return ERR_PTR(-ENOMEM);
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init_idle(tsk, cpu);
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return tsk;
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}
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void __init idle_thread_set_boot_cpu(void)
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{
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per_cpu(idle_threads, smp_processor_id()) = current;
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}
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/**
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* idle_init - Initialize the idle thread for a cpu
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* @cpu: The cpu for which the idle thread should be initialized
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*
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* Creates the thread if it does not exist.
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*/
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static inline void idle_init(unsigned int cpu)
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{
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struct task_struct *tsk = per_cpu(idle_threads, cpu);
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if (!tsk) {
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tsk = fork_idle(cpu);
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if (IS_ERR(tsk))
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pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
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else
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per_cpu(idle_threads, cpu) = tsk;
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}
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}
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/**
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* idle_threads_init - Initialize idle threads for all cpus
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*/
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void __init idle_threads_init(void)
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{
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unsigned int cpu, boot_cpu;
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boot_cpu = smp_processor_id();
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for_each_possible_cpu(cpu) {
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if (cpu != boot_cpu)
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idle_init(cpu);
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}
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}
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#endif
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#endif /* #ifdef CONFIG_SMP */
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static LIST_HEAD(hotplug_threads);
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static DEFINE_MUTEX(smpboot_threads_lock);
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struct smpboot_thread_data {
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unsigned int cpu;
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unsigned int status;
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struct smp_hotplug_thread *ht;
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};
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enum {
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HP_THREAD_NONE = 0,
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HP_THREAD_ACTIVE,
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HP_THREAD_PARKED,
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};
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/**
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* smpboot_thread_fn - percpu hotplug thread loop function
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* @data: thread data pointer
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*
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* Checks for thread stop and park conditions. Calls the necessary
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* setup, cleanup, park and unpark functions for the registered
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* thread.
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*
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* Returns 1 when the thread should exit, 0 otherwise.
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*/
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static int smpboot_thread_fn(void *data)
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{
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struct smpboot_thread_data *td = data;
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struct smp_hotplug_thread *ht = td->ht;
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while (1) {
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set_current_state(TASK_INTERRUPTIBLE);
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preempt_disable();
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if (kthread_should_stop()) {
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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if (ht->cleanup)
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ht->cleanup(td->cpu, cpu_online(td->cpu));
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kfree(td);
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return 0;
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}
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if (kthread_should_park()) {
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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if (ht->park && td->status == HP_THREAD_ACTIVE) {
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BUG_ON(td->cpu != smp_processor_id());
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ht->park(td->cpu);
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td->status = HP_THREAD_PARKED;
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}
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kthread_parkme();
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/* We might have been woken for stop */
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continue;
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}
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BUG_ON(td->cpu != smp_processor_id());
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/* Check for state change setup */
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switch (td->status) {
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case HP_THREAD_NONE:
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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if (ht->setup)
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ht->setup(td->cpu);
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td->status = HP_THREAD_ACTIVE;
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continue;
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case HP_THREAD_PARKED:
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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if (ht->unpark)
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ht->unpark(td->cpu);
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td->status = HP_THREAD_ACTIVE;
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continue;
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}
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if (!ht->thread_should_run(td->cpu)) {
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preempt_enable_no_resched();
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schedule();
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} else {
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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ht->thread_fn(td->cpu);
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}
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}
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}
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static int
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__smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
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{
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struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
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struct smpboot_thread_data *td;
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if (tsk)
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return 0;
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td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
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if (!td)
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return -ENOMEM;
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td->cpu = cpu;
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td->ht = ht;
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tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
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ht->thread_comm);
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if (IS_ERR(tsk)) {
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kfree(td);
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return PTR_ERR(tsk);
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}
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get_task_struct(tsk);
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*per_cpu_ptr(ht->store, cpu) = tsk;
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if (ht->create) {
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/*
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* Make sure that the task has actually scheduled out
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* into park position, before calling the create
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* callback. At least the migration thread callback
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* requires that the task is off the runqueue.
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*/
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if (!wait_task_inactive(tsk, TASK_PARKED))
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WARN_ON(1);
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else
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ht->create(cpu);
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}
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return 0;
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}
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int smpboot_create_threads(unsigned int cpu)
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{
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struct smp_hotplug_thread *cur;
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int ret = 0;
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mutex_lock(&smpboot_threads_lock);
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list_for_each_entry(cur, &hotplug_threads, list) {
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ret = __smpboot_create_thread(cur, cpu);
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if (ret)
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break;
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}
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mutex_unlock(&smpboot_threads_lock);
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return ret;
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}
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static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
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{
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struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
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if (ht->pre_unpark)
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ht->pre_unpark(cpu);
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kthread_unpark(tsk);
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}
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void smpboot_unpark_threads(unsigned int cpu)
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{
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struct smp_hotplug_thread *cur;
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mutex_lock(&smpboot_threads_lock);
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list_for_each_entry(cur, &hotplug_threads, list)
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smpboot_unpark_thread(cur, cpu);
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mutex_unlock(&smpboot_threads_lock);
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}
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static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
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{
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struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
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if (tsk && !ht->selfparking)
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kthread_park(tsk);
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}
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void smpboot_park_threads(unsigned int cpu)
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{
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struct smp_hotplug_thread *cur;
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mutex_lock(&smpboot_threads_lock);
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list_for_each_entry_reverse(cur, &hotplug_threads, list)
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smpboot_park_thread(cur, cpu);
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mutex_unlock(&smpboot_threads_lock);
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}
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static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
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{
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unsigned int cpu;
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/* We need to destroy also the parked threads of offline cpus */
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for_each_possible_cpu(cpu) {
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struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
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if (tsk) {
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kthread_stop(tsk);
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put_task_struct(tsk);
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*per_cpu_ptr(ht->store, cpu) = NULL;
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}
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}
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}
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/**
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* smpboot_register_percpu_thread - Register a per_cpu thread related to hotplug
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* @plug_thread: Hotplug thread descriptor
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*
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* Creates and starts the threads on all online cpus.
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*/
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int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
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{
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unsigned int cpu;
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int ret = 0;
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mutex_lock(&smpboot_threads_lock);
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for_each_online_cpu(cpu) {
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ret = __smpboot_create_thread(plug_thread, cpu);
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if (ret) {
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smpboot_destroy_threads(plug_thread);
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goto out;
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}
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smpboot_unpark_thread(plug_thread, cpu);
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}
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list_add(&plug_thread->list, &hotplug_threads);
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out:
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mutex_unlock(&smpboot_threads_lock);
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return ret;
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}
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EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
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/**
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* smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
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* @plug_thread: Hotplug thread descriptor
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*
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* Stops all threads on all possible cpus.
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*/
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void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
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{
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get_online_cpus();
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mutex_lock(&smpboot_threads_lock);
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list_del(&plug_thread->list);
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smpboot_destroy_threads(plug_thread);
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mutex_unlock(&smpboot_threads_lock);
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put_online_cpus();
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}
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EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
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