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Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 1026 |
1 files changed, 1026 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c new file mode 100644 index 0000000..d4dc69d --- /dev/null +++ b/kernel/workqueue.c @@ -0,0 +1,1026 @@ +/* + * 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 + * 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 */ + int rt; +#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_map_acquire(&cwq->wq->lockdep_map); + lock_map_acquire(&lockdep_map); + f(work); + lock_map_release(&lockdep_map); + lock_map_release(&cwq->wq->lockdep_map); + + 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_map_acquire(&wq->lockdep_map); + lock_map_release(&wq->lockdep_map); + 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_map_acquire(&cwq->wq->lockdep_map); + lock_map_release(&cwq->wq->lockdep_map); + + 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_map_acquire(&work->lockdep_map); + lock_map_release(&work->lockdep_map); + + 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 sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; + 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); + if (cwq->wq->rt) + sched_setscheduler_nocheck(p, SCHED_FIFO, ¶m); + 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, + int rt, + 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; + wq->rt = rt; + 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_map_acquire(&cwq->wq->lockdep_map); + lock_map_release(&cwq->wq->lockdep_map); + + 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; +} + +#ifdef CONFIG_SMP +struct work_for_cpu { + struct work_struct work; + long (*fn)(void *); + void *arg; + long ret; +}; + +static void do_work_for_cpu(struct work_struct *w) +{ + struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work); + + wfc->ret = wfc->fn(wfc->arg); +} + +/** + * work_on_cpu - run a function in user context on a particular cpu + * @cpu: the cpu to run on + * @fn: the function to run + * @arg: the function arg + * + * This will return -EINVAL in the cpu is not online, or the return value + * of @fn otherwise. + */ +long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) +{ + struct work_for_cpu wfc; + + INIT_WORK(&wfc.work, do_work_for_cpu); + wfc.fn = fn; + wfc.arg = arg; + get_online_cpus(); + if (unlikely(!cpu_online(cpu))) + wfc.ret = -EINVAL; + else { + schedule_work_on(cpu, &wfc.work); + flush_work(&wfc.work); + } + put_online_cpus(); + + return wfc.ret; +} +EXPORT_SYMBOL_GPL(work_on_cpu); +#endif /* CONFIG_SMP */ + +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); +} |
