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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323// SPDX-License-Identifier: GPL-2.0-only/* * 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/sched/task.h>#include <linux/export.h>#include <linux/percpu.h>#include <linux/kthread.h>#include <linux/smpboot.h>
#include "smpboot.h"
#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); 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 __always_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
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(); /* cleanup must mirror setup */ if (ht->cleanup && td->status != HP_THREAD_NONE) 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); } kthread_set_per_cpu(tsk, cpu); /* * Park the thread so that it could start right on the CPU * when it is available. */ kthread_park(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->selfparking) kthread_unpark(tsk);}
int 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); return 0;}
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);}
int 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); return 0;}
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_put(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;
cpus_read_lock(); 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); cpus_read_unlock(); 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){ cpus_read_lock(); mutex_lock(&smpboot_threads_lock); list_del(&plug_thread->list); smpboot_destroy_threads(plug_thread); mutex_unlock(&smpboot_threads_lock); cpus_read_unlock();}EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);