/* * linux/kernel/workqueue.c * * Generic mechanism for defining kernel helper threads for running * arbitrary tasks in process context. * * Started by Ingo Molnar, Copyright (C) 2002 * * Derived from the taskqueue/keventd code by: * * David Woodhouse <dwmw2@infradead.org> * Andrew Morton <andrewm@uow.edu.au> * Kai Petzke <wpp@marie.physik.tu-berlin.de> * Theodore Ts'o <tytso@mit.edu> * * Made to use alloc_percpu by Christoph Lameter. */ #include <linux/module.h> #include <linux/kernel.h> #include <linux/sched.h> #include <linux/init.h> #include <linux/signal.h> #include <linux/completion.h> #include <linux/workqueue.h> #include <linux/slab.h> #include <linux/cpu.h> #include <linux/notifier.h> #include <linux/kthread.h> #include <linux/hardirq.h> #include <linux/mempolicy.h> #include <linux/freezer.h> #include <linux/kallsyms.h> #include <linux/debug_locks.h> #include <linux/lockdep.h> /* * The per-CPU workqueue (if single thread, we always use the first * possible cpu). */ struct cpu_workqueue_struct { spinlock_t lock; struct list_head worklist; wait_queue_head_t more_work; struct work_struct *current_work; struct workqueue_struct *wq; struct task_struct *thread; int run_depth; /* Detect run_workqueue() recursion depth */ } ____cacheline_aligned; /* * The externally visible workqueue abstraction is an array of * per-CPU workqueues: */ struct workqueue_struct { struct cpu_workqueue_struct *cpu_wq; struct list_head list; const char *name; int singlethread; int freezeable; /* Freeze threads during suspend */ #ifdef CONFIG_LOCKDEP struct lockdep_map lockdep_map; #endif }; /* Serializes the accesses to the list of workqueues. */ static DEFINE_SPINLOCK(workqueue_lock); static LIST_HEAD(workqueues); static int singlethread_cpu __read_mostly; static cpumask_t cpu_singlethread_map __read_mostly; /* * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD * flushes cwq->worklist. This means that flush_workqueue/wait_on_work * which comes in between can't use for_each_online_cpu(). We could * use cpu_possible_map, the cpumask below is more a documentation * than optimization. */ static cpumask_t cpu_populated_map __read_mostly; /* If it's single threaded, it isn't in the list of workqueues. */ static inline int is_single_threaded(struct workqueue_struct *wq) { return wq->singlethread; } static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq) { return is_single_threaded(wq) ? &cpu_singlethread_map : &cpu_populated_map; } static struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu) { if (unlikely(is_single_threaded(wq))) cpu = singlethread_cpu; return per_cpu_ptr(wq->cpu_wq, cpu); } /* * Set the workqueue on which a work item is to be run * - Must *only* be called if the pending flag is set */ static inline void set_wq_data(struct work_struct *work, struct cpu_workqueue_struct *cwq) { unsigned long new; BUG_ON(!work_pending(work)); new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING); new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work); atomic_long_set(&work->data, new); } static inline struct cpu_workqueue_struct *get_wq_data(struct work_struct *work) { return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK); } static void insert_work(struct cpu_workqueue_struct *cwq, struct work_struct *work, struct list_head *head) { set_wq_data(work, cwq); /* * Ensure that we get the right work->data if we see the * result of list_add() below, see try_to_grab_pending(). */ smp_wmb(); list_add_tail(&work->entry, head); wake_up(&cwq->more_work); } static void __queue_work(struct cpu_workqueue_struct *cwq, struct work_struct *work) { unsigned long flags; spin_lock_irqsave(&cwq->lock, flags); insert_work(cwq, work, &cwq->worklist); spin_unlock_irqrestore(&cwq->lock, flags); } /** * queue_work - queue work on a workqueue * @wq: workqueue to use * @work: work to queue * * Returns 0 if @work was already on a queue, non-zero otherwise. * * We queue the work to the CPU on which it was submitted, but if the CPU dies * it can be processed by another CPU. */ int queue_work(struct workqueue_struct *wq, struct work_struct *work) { int ret; ret = queue_work_on(get_cpu(), wq, work); put_cpu(); return ret; } EXPORT_SYMBOL_GPL(queue_work); /** * queue_work_on - queue work on specific cpu * @cpu: CPU number to execute work on * @wq: workqueue to use * @work: work to queue * * Returns 0 if @work was already on a queue, non-zero otherwise. * * We queue the work to a specific CPU, the caller must ensure it * can't go away. */ int queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work) { int ret = 0; if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) { BUG_ON(!list_empty(&work->entry)); __queue_work(wq_per_cpu(wq, cpu), work); ret = 1; } return ret; } EXPORT_SYMBOL_GPL(queue_work_on); static void delayed_work_timer_fn(unsigned long __data) { struct delayed_work *dwork = (struct delayed_work *)__data; struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work); struct workqueue_struct *wq = cwq->wq; __queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work); } /** * queue_delayed_work - queue work on a workqueue after delay * @wq: workqueue to use * @dwork: delayable work to queue * @delay: number of jiffies to wait before queueing * * Returns 0 if @work was already on a queue, non-zero otherwise. */ int queue_delayed_work(struct workqueue_struct *wq, struct delayed_work *dwork, unsigned long delay) { if (delay == 0) return queue_work(wq, &dwork->work); return queue_delayed_work_on(-1, wq, dwork, delay); } EXPORT_SYMBOL_GPL(queue_delayed_work); /** * queue_delayed_work_on - queue work on specific CPU after delay * @cpu: CPU number to execute work on * @wq: workqueue to use * @dwork: work to queue * @delay: number of jiffies to wait before queueing * * Returns 0 if @work was already on a queue, non-zero otherwise. */ int queue_delayed_work_on(int cpu, struct workqueue_struct *wq, struct delayed_work *dwork, unsigned long delay) { int ret = 0; struct timer_list *timer = &dwork->timer; struct work_struct *work = &dwork->work; if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) { BUG_ON(timer_pending(timer)); BUG_ON(!list_empty(&work->entry)); timer_stats_timer_set_start_info(&dwork->timer); /* This stores cwq for the moment, for the timer_fn */ set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id())); timer->expires = jiffies + delay; timer->data = (unsigned long)dwork; timer->function = delayed_work_timer_fn; if (unlikely(cpu >= 0)) add_timer_on(timer, cpu); else add_timer(timer); ret = 1; } return ret; } EXPORT_SYMBOL_GPL(queue_delayed_work_on); static void run_workqueue(struct cpu_workqueue_struct *cwq) { spin_lock_irq(&cwq->lock); cwq->run_depth++; if (cwq->run_depth > 3) { /* morton gets to eat his hat */ printk("%s: recursion depth exceeded: %d\n", __func__, cwq->run_depth); dump_stack(); } while (!list_empty(&cwq->worklist)) { struct work_struct *work = list_entry(cwq->worklist.next, struct work_struct, entry); work_func_t f = work->func; #ifdef CONFIG_LOCKDEP /* * It is permissible to free the struct work_struct * from inside the function that is called from it, * this we need to take into account for lockdep too. * To avoid bogus "held lock freed" warnings as well * as problems when looking into work->lockdep_map, * make a copy and use that here. */ struct lockdep_map lockdep_map = work->lockdep_map; #endif cwq->current_work = work; list_del_init(cwq->worklist.next); spin_unlock_irq(&cwq->lock); BUG_ON(get_wq_data(work) != cwq); work_clear_pending(work); lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_); lock_acquire(&lockdep_map, 0, 0, 0, 2, _THIS_IP_); f(work); lock_release(&lockdep_map, 1, _THIS_IP_); lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_); if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { printk(KERN_ERR "BUG: workqueue leaked lock or atomic: " "%s/0x%08x/%d\n", current->comm, preempt_count(), task_pid_nr(current)); printk(KERN_ERR " last function: "); print_symbol("%s\n", (unsigned long)f); debug_show_held_locks(current); dump_stack(); } spin_lock_irq(&cwq->lock); cwq->current_work = NULL; } cwq->run_depth--; spin_unlock_irq(&cwq->lock); } static int worker_thread(void *__cwq) { struct cpu_workqueue_struct *cwq = __cwq; DEFINE_WAIT(wait); if (cwq->wq->freezeable) set_freezable(); set_user_nice(current, -5); for (;;) { prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE); if (!freezing(current) && !kthread_should_stop() && list_empty(&cwq->worklist)) schedule(); finish_wait(&cwq->more_work, &wait); try_to_freeze(); if (kthread_should_stop()) break; run_workqueue(cwq); } return 0; } struct wq_barrier { struct work_struct work; struct completion done; }; static void wq_barrier_func(struct work_struct *work) { struct wq_barrier *barr = container_of(work, struct wq_barrier, work); complete(&barr->done); } static void insert_wq_barrier(struct cpu_workqueue_struct *cwq, struct wq_barrier *barr, struct list_head *head) { INIT_WORK(&barr->work, wq_barrier_func); __set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work)); init_completion(&barr->done); insert_work(cwq, &barr->work, head); } static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq) { int active; if (cwq->thread == current) { /* * Probably keventd trying to flush its own queue. So simply run * it by hand rather than deadlocking. */ run_workqueue(cwq); active = 1; } else { struct wq_barrier barr; active = 0; spin_lock_irq(&cwq->lock); if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) { insert_wq_barrier(cwq, &barr, &cwq->worklist); active = 1; } spin_unlock_irq(&cwq->lock); if (active) wait_for_completion(&barr.done); } return active; } /** * flush_workqueue - ensure that any scheduled work has run to completion. * @wq: workqueue to flush * * Forces execution of the workqueue and blocks until its completion. * This is typically used in driver shutdown handlers. * * We sleep until all works which were queued on entry have been handled, * but we are not livelocked by new incoming ones. * * This function used to run the workqueues itself. Now we just wait for the * helper threads to do it. */ void flush_workqueue(struct workqueue_struct *wq) { const cpumask_t *cpu_map = wq_cpu_map(wq); int cpu; might_sleep(); lock_acquire(&wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_); lock_release(&wq->lockdep_map, 1, _THIS_IP_); for_each_cpu_mask_nr(cpu, *cpu_map) flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu)); } EXPORT_SYMBOL_GPL(flush_workqueue); /** * flush_work - block until a work_struct's callback has terminated * @work: the work which is to be flushed * * Returns false if @work has already terminated. * * It is expected that, prior to calling flush_work(), the caller has * arranged for the work to not be requeued, otherwise it doesn't make * sense to use this function. */ int flush_work(struct work_struct *work) { struct cpu_workqueue_struct *cwq; struct list_head *prev; struct wq_barrier barr; might_sleep(); cwq = get_wq_data(work); if (!cwq) return 0; lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_); lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_); prev = NULL; spin_lock_irq(&cwq->lock); if (!list_empty(&work->entry)) { /* * See the comment near try_to_grab_pending()->smp_rmb(). * If it was re-queued under us we are not going to wait. */ smp_rmb(); if (unlikely(cwq != get_wq_data(work))) goto out; prev = &work->entry; } else { if (cwq->current_work != work) goto out; prev = &cwq->worklist; } insert_wq_barrier(cwq, &barr, prev->next); out: spin_unlock_irq(&cwq->lock); if (!prev) return 0; wait_for_completion(&barr.done); return 1; } EXPORT_SYMBOL_GPL(flush_work); /* * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit, * so this work can't be re-armed in any way. */ static int try_to_grab_pending(struct work_struct *work) { struct cpu_workqueue_struct *cwq; int ret = -1; if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) return 0; /* * The queueing is in progress, or it is already queued. Try to * steal it from ->worklist without clearing WORK_STRUCT_PENDING. */ cwq = get_wq_data(work); if (!cwq) return ret; spin_lock_irq(&cwq->lock); if (!list_empty(&work->entry)) { /* * This work is queued, but perhaps we locked the wrong cwq. * In that case we must see the new value after rmb(), see * insert_work()->wmb(). */ smp_rmb(); if (cwq == get_wq_data(work)) { list_del_init(&work->entry); ret = 1; } } spin_unlock_irq(&cwq->lock); return ret; } static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq, struct work_struct *work) { struct wq_barrier barr; int running = 0; spin_lock_irq(&cwq->lock); if (unlikely(cwq->current_work == work)) { insert_wq_barrier(cwq, &barr, cwq->worklist.next); running = 1; } spin_unlock_irq(&cwq->lock); if (unlikely(running)) wait_for_completion(&barr.done); } static void wait_on_work(struct work_struct *work) { struct cpu_workqueue_struct *cwq; struct workqueue_struct *wq; const cpumask_t *cpu_map; int cpu; might_sleep(); lock_acquire(&work->lockdep_map, 0, 0, 0, 2, _THIS_IP_); lock_release(&work->lockdep_map, 1, _THIS_IP_); cwq = get_wq_data(work); if (!cwq) return; wq = cwq->wq; cpu_map = wq_cpu_map(wq); for_each_cpu_mask_nr(cpu, *cpu_map) wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work); } static int __cancel_work_timer(struct work_struct *work, struct timer_list* timer) { int ret; do { ret = (timer && likely(del_timer(timer))); if (!ret) ret = try_to_grab_pending(work); wait_on_work(work); } while (unlikely(ret < 0)); work_clear_pending(work); return ret; } /** * cancel_work_sync - block until a work_struct's callback has terminated * @work: the work which is to be flushed * * Returns true if @work was pending. * * cancel_work_sync() will cancel the work if it is queued. If the work's * callback appears to be running, cancel_work_sync() will block until it * has completed. * * It is possible to use this function if the work re-queues itself. It can * cancel the work even if it migrates to another workqueue, however in that * case it only guarantees that work->func() has completed on the last queued * workqueue. * * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not * pending, otherwise it goes into a busy-wait loop until the timer expires. * * The caller must ensure that workqueue_struct on which this work was last * queued can't be destroyed before this function returns. */ int cancel_work_sync(struct work_struct *work) { return __cancel_work_timer(work, NULL); } EXPORT_SYMBOL_GPL(cancel_work_sync); /** * cancel_delayed_work_sync - reliably kill off a delayed work. * @dwork: the delayed work struct * * Returns true if @dwork was pending. * * It is possible to use this function if @dwork rearms itself via queue_work() * or queue_delayed_work(). See also the comment for cancel_work_sync(). */ int cancel_delayed_work_sync(struct delayed_work *dwork) { return __cancel_work_timer(&dwork->work, &dwork->timer); } EXPORT_SYMBOL(cancel_delayed_work_sync); static struct workqueue_struct *keventd_wq __read_mostly; /** * schedule_work - put work task in global workqueue * @work: job to be done * * This puts a job in the kernel-global workqueue. */ int schedule_work(struct work_struct *work) { return queue_work(keventd_wq, work); } EXPORT_SYMBOL(schedule_work); /* * schedule_work_on - put work task on a specific cpu * @cpu: cpu to put the work task on * @work: job to be done * * This puts a job on a specific cpu */ int schedule_work_on(int cpu, struct work_struct *work) { return queue_work_on(cpu, keventd_wq, work); } EXPORT_SYMBOL(schedule_work_on); /** * schedule_delayed_work - put work task in global workqueue after delay * @dwork: job to be done * @delay: number of jiffies to wait or 0 for immediate execution * * After waiting for a given time this puts a job in the kernel-global * workqueue. */ int schedule_delayed_work(struct delayed_work *dwork, unsigned long delay) { return queue_delayed_work(keventd_wq, dwork, delay); } EXPORT_SYMBOL(schedule_delayed_work); /** * schedule_delayed_work_on - queue work in global workqueue on CPU after delay * @cpu: cpu to use * @dwork: job to be done * @delay: number of jiffies to wait * * After waiting for a given time this puts a job in the kernel-global * workqueue on the specified CPU. */ int schedule_delayed_work_on(int cpu, struct delayed_work *dwork, unsigned long delay) { return queue_delayed_work_on(cpu, keventd_wq, dwork, delay); } EXPORT_SYMBOL(schedule_delayed_work_on); /** * schedule_on_each_cpu - call a function on each online CPU from keventd * @func: the function to call * * Returns zero on success. * Returns -ve errno on failure. * * schedule_on_each_cpu() is very slow. */ int schedule_on_each_cpu(work_func_t func) { int cpu; struct work_struct *works; works = alloc_percpu(struct work_struct); if (!works) return -ENOMEM; get_online_cpus(); for_each_online_cpu(cpu) { struct work_struct *work = per_cpu_ptr(works, cpu); INIT_WORK(work, func); schedule_work_on(cpu, work); } for_each_online_cpu(cpu) flush_work(per_cpu_ptr(works, cpu)); put_online_cpus(); free_percpu(works); return 0; } void flush_scheduled_work(void) { flush_workqueue(keventd_wq); } EXPORT_SYMBOL(flush_scheduled_work); /** * execute_in_process_context - reliably execute the routine with user context * @fn: the function to execute * @ew: guaranteed storage for the execute work structure (must * be available when the work executes) * * Executes the function immediately if process context is available, * otherwise schedules the function for delayed execution. * * Returns: 0 - function was executed * 1 - function was scheduled for execution */ int execute_in_process_context(work_func_t fn, struct execute_work *ew) { if (!in_interrupt()) { fn(&ew->work); return 0; } INIT_WORK(&ew->work, fn); schedule_work(&ew->work); return 1; } EXPORT_SYMBOL_GPL(execute_in_process_context); int keventd_up(void) { return keventd_wq != NULL; } int current_is_keventd(void) { struct cpu_workqueue_struct *cwq; int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */ int ret = 0; BUG_ON(!keventd_wq); cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu); if (current == cwq->thread) ret = 1; return ret; } static struct cpu_workqueue_struct * init_cpu_workqueue(struct workqueue_struct *wq, int cpu) { struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu); cwq->wq = wq; spin_lock_init(&cwq->lock); INIT_LIST_HEAD(&cwq->worklist); init_waitqueue_head(&cwq->more_work); return cwq; } static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu) { struct workqueue_struct *wq = cwq->wq; const char *fmt = is_single_threaded(wq) ? "%s" : "%s/%d"; struct task_struct *p; p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu); /* * Nobody can add the work_struct to this cwq, * if (caller is __create_workqueue) * nobody should see this wq * else // caller is CPU_UP_PREPARE * cpu is not on cpu_online_map * so we can abort safely. */ if (IS_ERR(p)) return PTR_ERR(p); cwq->thread = p; return 0; } static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu) { struct task_struct *p = cwq->thread; if (p != NULL) { if (cpu >= 0) kthread_bind(p, cpu); wake_up_process(p); } } struct workqueue_struct *__create_workqueue_key(const char *name, int singlethread, int freezeable, struct lock_class_key *key, const char *lock_name) { struct workqueue_struct *wq; struct cpu_workqueue_struct *cwq; int err = 0, cpu; wq = kzalloc(sizeof(*wq), GFP_KERNEL); if (!wq) return NULL; wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct); if (!wq->cpu_wq) { kfree(wq); return NULL; } wq->name = name; lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); wq->singlethread = singlethread; wq->freezeable = freezeable; INIT_LIST_HEAD(&wq->list); if (singlethread) { cwq = init_cpu_workqueue(wq, singlethread_cpu); err = create_workqueue_thread(cwq, singlethread_cpu); start_workqueue_thread(cwq, -1); } else { cpu_maps_update_begin(); /* * We must place this wq on list even if the code below fails. * cpu_down(cpu) can remove cpu from cpu_populated_map before * destroy_workqueue() takes the lock, in that case we leak * cwq[cpu]->thread. */ spin_lock(&workqueue_lock); list_add(&wq->list, &workqueues); spin_unlock(&workqueue_lock); /* * We must initialize cwqs for each possible cpu even if we * are going to call destroy_workqueue() finally. Otherwise * cpu_up() can hit the uninitialized cwq once we drop the * lock. */ for_each_possible_cpu(cpu) { cwq = init_cpu_workqueue(wq, cpu); if (err || !cpu_online(cpu)) continue; err = create_workqueue_thread(cwq, cpu); start_workqueue_thread(cwq, cpu); } cpu_maps_update_done(); } if (err) { destroy_workqueue(wq); wq = NULL; } return wq; } EXPORT_SYMBOL_GPL(__create_workqueue_key); static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq) { /* * Our caller is either destroy_workqueue() or CPU_POST_DEAD, * cpu_add_remove_lock protects cwq->thread. */ if (cwq->thread == NULL) return; lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_); lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_); flush_cpu_workqueue(cwq); /* * If the caller is CPU_POST_DEAD and cwq->worklist was not empty, * a concurrent flush_workqueue() can insert a barrier after us. * However, in that case run_workqueue() won't return and check * kthread_should_stop() until it flushes all work_struct's. * When ->worklist becomes empty it is safe to exit because no * more work_structs can be queued on this cwq: flush_workqueue * checks list_empty(), and a "normal" queue_work() can't use * a dead CPU. */ kthread_stop(cwq->thread); cwq->thread = NULL; } /** * destroy_workqueue - safely terminate a workqueue * @wq: target workqueue * * Safely destroy a workqueue. All work currently pending will be done first. */ void destroy_workqueue(struct workqueue_struct *wq) { const cpumask_t *cpu_map = wq_cpu_map(wq); int cpu; cpu_maps_update_begin(); spin_lock(&workqueue_lock); list_del(&wq->list); spin_unlock(&workqueue_lock); for_each_cpu_mask_nr(cpu, *cpu_map) cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu)); cpu_maps_update_done(); free_percpu(wq->cpu_wq); kfree(wq); } EXPORT_SYMBOL_GPL(destroy_workqueue); static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { unsigned int cpu = (unsigned long)hcpu; struct cpu_workqueue_struct *cwq; struct workqueue_struct *wq; int ret = NOTIFY_OK; action &= ~CPU_TASKS_FROZEN; switch (action) { case CPU_UP_PREPARE: cpu_set(cpu, cpu_populated_map); } undo: list_for_each_entry(wq, &workqueues, list) { cwq = per_cpu_ptr(wq->cpu_wq, cpu); switch (action) { case CPU_UP_PREPARE: if (!create_workqueue_thread(cwq, cpu)) break; printk(KERN_ERR "workqueue [%s] for %i failed\n", wq->name, cpu); action = CPU_UP_CANCELED; ret = NOTIFY_BAD; goto undo; case CPU_ONLINE: start_workqueue_thread(cwq, cpu); break; case CPU_UP_CANCELED: start_workqueue_thread(cwq, -1); case CPU_POST_DEAD: cleanup_workqueue_thread(cwq); break; } } switch (action) { case CPU_UP_CANCELED: case CPU_POST_DEAD: cpu_clear(cpu, cpu_populated_map); } return ret; } void __init init_workqueues(void) { cpu_populated_map = cpu_online_map; singlethread_cpu = first_cpu(cpu_possible_map); cpu_singlethread_map = cpumask_of_cpu(singlethread_cpu); hotcpu_notifier(workqueue_cpu_callback, 0); keventd_wq = create_workqueue("events"); BUG_ON(!keventd_wq); }