/* * 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 * Andrew Morton * Kai Petzke * Theodore Ts'o * * Made to use alloc_percpu by Christoph Lameter. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include enum { /* global_cwq flags */ GCWQ_FREEZING = 1 << 3, /* freeze in progress */ /* worker flags */ WORKER_STARTED = 1 << 0, /* started */ WORKER_DIE = 1 << 1, /* die die die */ WORKER_IDLE = 1 << 2, /* is idle */ WORKER_ROGUE = 1 << 4, /* not bound to any cpu */ /* gcwq->trustee_state */ TRUSTEE_START = 0, /* start */ TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */ TRUSTEE_BUTCHER = 2, /* butcher workers */ TRUSTEE_RELEASE = 3, /* release workers */ TRUSTEE_DONE = 4, /* trustee is done */ BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */ BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER, BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1, TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */ }; /* * Structure fields follow one of the following exclusion rules. * * I: Set during initialization and read-only afterwards. * * L: gcwq->lock protected. Access with gcwq->lock held. * * F: wq->flush_mutex protected. * * W: workqueue_lock protected. */ struct global_cwq; struct cpu_workqueue_struct; struct worker { /* on idle list while idle, on busy hash table while busy */ union { struct list_head entry; /* L: while idle */ struct hlist_node hentry; /* L: while busy */ }; struct work_struct *current_work; /* L: work being processed */ struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */ struct list_head scheduled; /* L: scheduled works */ struct task_struct *task; /* I: worker task */ struct global_cwq *gcwq; /* I: the associated gcwq */ struct cpu_workqueue_struct *cwq; /* I: the associated cwq */ unsigned int flags; /* L: flags */ int id; /* I: worker id */ }; /* * Global per-cpu workqueue. */ struct global_cwq { spinlock_t lock; /* the gcwq lock */ unsigned int cpu; /* I: the associated cpu */ unsigned int flags; /* L: GCWQ_* flags */ int nr_workers; /* L: total number of workers */ int nr_idle; /* L: currently idle ones */ /* workers are chained either in the idle_list or busy_hash */ struct list_head idle_list; /* L: list of idle workers */ struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE]; /* L: hash of busy workers */ struct ida worker_ida; /* L: for worker IDs */ struct task_struct *trustee; /* L: for gcwq shutdown */ unsigned int trustee_state; /* L: trustee state */ wait_queue_head_t trustee_wait; /* trustee wait */ } ____cacheline_aligned_in_smp; /* * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of * work_struct->data are used for flags and thus cwqs need to be * aligned at two's power of the number of flag bits. */ struct cpu_workqueue_struct { struct global_cwq *gcwq; /* I: the associated gcwq */ struct list_head worklist; struct worker *worker; struct workqueue_struct *wq; /* I: the owning workqueue */ int work_color; /* L: current color */ int flush_color; /* L: flushing color */ int nr_in_flight[WORK_NR_COLORS]; /* L: nr of in_flight works */ int nr_active; /* L: nr of active works */ int max_active; /* L: max active works */ struct list_head delayed_works; /* L: delayed works */ }; /* * Structure used to wait for workqueue flush. */ struct wq_flusher { struct list_head list; /* F: list of flushers */ int flush_color; /* F: flush color waiting for */ struct completion done; /* flush completion */ }; /* * The externally visible workqueue abstraction is an array of * per-CPU workqueues: */ struct workqueue_struct { unsigned int flags; /* I: WQ_* flags */ struct cpu_workqueue_struct *cpu_wq; /* I: cwq's */ struct list_head list; /* W: list of all workqueues */ struct mutex flush_mutex; /* protects wq flushing */ int work_color; /* F: current work color */ int flush_color; /* F: current flush color */ atomic_t nr_cwqs_to_flush; /* flush in progress */ struct wq_flusher *first_flusher; /* F: first flusher */ struct list_head flusher_queue; /* F: flush waiters */ struct list_head flusher_overflow; /* F: flush overflow list */ unsigned long single_cpu; /* cpu for single cpu wq */ int saved_max_active; /* I: saved cwq max_active */ const char *name; /* I: workqueue name */ #ifdef CONFIG_LOCKDEP struct lockdep_map lockdep_map; #endif }; #define for_each_busy_worker(worker, i, pos, gcwq) \ for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \ hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry) #ifdef CONFIG_DEBUG_OBJECTS_WORK static struct debug_obj_descr work_debug_descr; /* * fixup_init is called when: * - an active object is initialized */ static int work_fixup_init(void *addr, enum debug_obj_state state) { struct work_struct *work = addr; switch (state) { case ODEBUG_STATE_ACTIVE: cancel_work_sync(work); debug_object_init(work, &work_debug_descr); return 1; default: return 0; } } /* * fixup_activate is called when: * - an active object is activated * - an unknown object is activated (might be a statically initialized object) */ static int work_fixup_activate(void *addr, enum debug_obj_state state) { struct work_struct *work = addr; switch (state) { case ODEBUG_STATE_NOTAVAILABLE: /* * This is not really a fixup. The work struct was * statically initialized. We just make sure that it * is tracked in the object tracker. */ if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) { debug_object_init(work, &work_debug_descr); debug_object_activate(work, &work_debug_descr); return 0; } WARN_ON_ONCE(1); return 0; case ODEBUG_STATE_ACTIVE: WARN_ON(1); default: return 0; } } /* * fixup_free is called when: * - an active object is freed */ static int work_fixup_free(void *addr, enum debug_obj_state state) { struct work_struct *work = addr; switch (state) { case ODEBUG_STATE_ACTIVE: cancel_work_sync(work); debug_object_free(work, &work_debug_descr); return 1; default: return 0; } } static struct debug_obj_descr work_debug_descr = { .name = "work_struct", .fixup_init = work_fixup_init, .fixup_activate = work_fixup_activate, .fixup_free = work_fixup_free, }; static inline void debug_work_activate(struct work_struct *work) { debug_object_activate(work, &work_debug_descr); } static inline void debug_work_deactivate(struct work_struct *work) { debug_object_deactivate(work, &work_debug_descr); } void __init_work(struct work_struct *work, int onstack) { if (onstack) debug_object_init_on_stack(work, &work_debug_descr); else debug_object_init(work, &work_debug_descr); } EXPORT_SYMBOL_GPL(__init_work); void destroy_work_on_stack(struct work_struct *work) { debug_object_free(work, &work_debug_descr); } EXPORT_SYMBOL_GPL(destroy_work_on_stack); #else static inline void debug_work_activate(struct work_struct *work) { } static inline void debug_work_deactivate(struct work_struct *work) { } #endif /* Serializes the accesses to the list of workqueues. */ static DEFINE_SPINLOCK(workqueue_lock); static LIST_HEAD(workqueues); static bool workqueue_freezing; /* W: have wqs started freezing? */ static DEFINE_PER_CPU(struct global_cwq, global_cwq); static int worker_thread(void *__worker); static struct global_cwq *get_gcwq(unsigned int cpu) { return &per_cpu(global_cwq, cpu); } static struct cpu_workqueue_struct *get_cwq(unsigned int cpu, struct workqueue_struct *wq) { return per_cpu_ptr(wq->cpu_wq, cpu); } static unsigned int work_color_to_flags(int color) { return color << WORK_STRUCT_COLOR_SHIFT; } static int get_work_color(struct work_struct *work) { return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) & ((1 << WORK_STRUCT_COLOR_BITS) - 1); } static int work_next_color(int color) { return (color + 1) % WORK_NR_COLORS; } /* * 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 extra_flags) { BUG_ON(!work_pending(work)); atomic_long_set(&work->data, (unsigned long)cwq | work_static(work) | WORK_STRUCT_PENDING | extra_flags); } /* * Clear WORK_STRUCT_PENDING and the workqueue on which it was queued. */ static inline void clear_wq_data(struct work_struct *work) { atomic_long_set(&work->data, work_static(work)); } 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); } /** * busy_worker_head - return the busy hash head for a work * @gcwq: gcwq of interest * @work: work to be hashed * * Return hash head of @gcwq for @work. * * CONTEXT: * spin_lock_irq(gcwq->lock). * * RETURNS: * Pointer to the hash head. */ static struct hlist_head *busy_worker_head(struct global_cwq *gcwq, struct work_struct *work) { const int base_shift = ilog2(sizeof(struct work_struct)); unsigned long v = (unsigned long)work; /* simple shift and fold hash, do we need something better? */ v >>= base_shift; v += v >> BUSY_WORKER_HASH_ORDER; v &= BUSY_WORKER_HASH_MASK; return &gcwq->busy_hash[v]; } /** * __find_worker_executing_work - find worker which is executing a work * @gcwq: gcwq of interest * @bwh: hash head as returned by busy_worker_head() * @work: work to find worker for * * Find a worker which is executing @work on @gcwq. @bwh should be * the hash head obtained by calling busy_worker_head() with the same * work. * * CONTEXT: * spin_lock_irq(gcwq->lock). * * RETURNS: * Pointer to worker which is executing @work if found, NULL * otherwise. */ static struct worker *__find_worker_executing_work(struct global_cwq *gcwq, struct hlist_head *bwh, struct work_struct *work) { struct worker *worker; struct hlist_node *tmp; hlist_for_each_entry(worker, tmp, bwh, hentry) if (worker->current_work == work) return worker; return NULL; } /** * find_worker_executing_work - find worker which is executing a work * @gcwq: gcwq of interest * @work: work to find worker for * * Find a worker which is executing @work on @gcwq. This function is * identical to __find_worker_executing_work() except that this * function calculates @bwh itself. * * CONTEXT: * spin_lock_irq(gcwq->lock). * * RETURNS: * Pointer to worker which is executing @work if found, NULL * otherwise. */ static struct worker *find_worker_executing_work(struct global_cwq *gcwq, struct work_struct *work) { return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work), work); } /** * insert_work - insert a work into cwq * @cwq: cwq @work belongs to * @work: work to insert * @head: insertion point * @extra_flags: extra WORK_STRUCT_* flags to set * * Insert @work into @cwq after @head. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void insert_work(struct cpu_workqueue_struct *cwq, struct work_struct *work, struct list_head *head, unsigned int extra_flags) { /* we own @work, set data and link */ set_wq_data(work, cwq, extra_flags); /* * 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_process(cwq->worker->task); } /** * cwq_unbind_single_cpu - unbind cwq from single cpu workqueue processing * @cwq: cwq to unbind * * Try to unbind @cwq from single cpu workqueue processing. If * @cwq->wq is frozen, unbind is delayed till the workqueue is thawed. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void cwq_unbind_single_cpu(struct cpu_workqueue_struct *cwq) { struct workqueue_struct *wq = cwq->wq; struct global_cwq *gcwq = cwq->gcwq; BUG_ON(wq->single_cpu != gcwq->cpu); /* * Unbind from workqueue if @cwq is not frozen. If frozen, * thaw_workqueues() will either restart processing on this * cpu or unbind if empty. This keeps works queued while * frozen fully ordered and flushable. */ if (likely(!(gcwq->flags & GCWQ_FREEZING))) { smp_wmb(); /* paired with cmpxchg() in __queue_work() */ wq->single_cpu = NR_CPUS; } } static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, struct work_struct *work) { struct global_cwq *gcwq; struct cpu_workqueue_struct *cwq; struct list_head *worklist; unsigned long flags; bool arbitrate; debug_work_activate(work); /* determine gcwq to use */ if (!(wq->flags & WQ_SINGLE_CPU)) { /* just use the requested cpu for multicpu workqueues */ gcwq = get_gcwq(cpu); spin_lock_irqsave(&gcwq->lock, flags); } else { unsigned int req_cpu = cpu; /* * It's a bit more complex for single cpu workqueues. * We first need to determine which cpu is going to be * used. If no cpu is currently serving this * workqueue, arbitrate using atomic accesses to * wq->single_cpu; otherwise, use the current one. */ retry: cpu = wq->single_cpu; arbitrate = cpu == NR_CPUS; if (arbitrate) cpu = req_cpu; gcwq = get_gcwq(cpu); spin_lock_irqsave(&gcwq->lock, flags); /* * The following cmpxchg() is a full barrier paired * with smp_wmb() in cwq_unbind_single_cpu() and * guarantees that all changes to wq->st_* fields are * visible on the new cpu after this point. */ if (arbitrate) cmpxchg(&wq->single_cpu, NR_CPUS, cpu); if (unlikely(wq->single_cpu != cpu)) { spin_unlock_irqrestore(&gcwq->lock, flags); goto retry; } } /* gcwq determined, get cwq and queue */ cwq = get_cwq(gcwq->cpu, wq); BUG_ON(!list_empty(&work->entry)); cwq->nr_in_flight[cwq->work_color]++; if (likely(cwq->nr_active < cwq->max_active)) { cwq->nr_active++; worklist = &cwq->worklist; } else worklist = &cwq->delayed_works; insert_work(cwq, work, worklist, work_color_to_flags(cwq->work_color)); spin_unlock_irqrestore(&gcwq->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_BIT, work_data_bits(work))) { __queue_work(cpu, wq, 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); __queue_work(smp_processor_id(), cwq->wq, &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_BIT, 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, get_cwq(raw_smp_processor_id(), wq), 0); 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); /** * worker_enter_idle - enter idle state * @worker: worker which is entering idle state * * @worker is entering idle state. Update stats and idle timer if * necessary. * * LOCKING: * spin_lock_irq(gcwq->lock). */ static void worker_enter_idle(struct worker *worker) { struct global_cwq *gcwq = worker->gcwq; BUG_ON(worker->flags & WORKER_IDLE); BUG_ON(!list_empty(&worker->entry) && (worker->hentry.next || worker->hentry.pprev)); worker->flags |= WORKER_IDLE; gcwq->nr_idle++; /* idle_list is LIFO */ list_add(&worker->entry, &gcwq->idle_list); if (unlikely(worker->flags & WORKER_ROGUE)) wake_up_all(&gcwq->trustee_wait); } /** * worker_leave_idle - leave idle state * @worker: worker which is leaving idle state * * @worker is leaving idle state. Update stats. * * LOCKING: * spin_lock_irq(gcwq->lock). */ static void worker_leave_idle(struct worker *worker) { struct global_cwq *gcwq = worker->gcwq; BUG_ON(!(worker->flags & WORKER_IDLE)); worker->flags &= ~WORKER_IDLE; gcwq->nr_idle--; list_del_init(&worker->entry); } static struct worker *alloc_worker(void) { struct worker *worker; worker = kzalloc(sizeof(*worker), GFP_KERNEL); if (worker) { INIT_LIST_HEAD(&worker->entry); INIT_LIST_HEAD(&worker->scheduled); } return worker; } /** * create_worker - create a new workqueue worker * @cwq: cwq the new worker will belong to * @bind: whether to set affinity to @cpu or not * * Create a new worker which is bound to @cwq. The returned worker * can be started by calling start_worker() or destroyed using * destroy_worker(). * * CONTEXT: * Might sleep. Does GFP_KERNEL allocations. * * RETURNS: * Pointer to the newly created worker. */ static struct worker *create_worker(struct cpu_workqueue_struct *cwq, bool bind) { struct global_cwq *gcwq = cwq->gcwq; int id = -1; struct worker *worker = NULL; spin_lock_irq(&gcwq->lock); while (ida_get_new(&gcwq->worker_ida, &id)) { spin_unlock_irq(&gcwq->lock); if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL)) goto fail; spin_lock_irq(&gcwq->lock); } spin_unlock_irq(&gcwq->lock); worker = alloc_worker(); if (!worker) goto fail; worker->gcwq = gcwq; worker->cwq = cwq; worker->id = id; worker->task = kthread_create(worker_thread, worker, "kworker/%u:%d", gcwq->cpu, id); if (IS_ERR(worker->task)) goto fail; /* * A rogue worker will become a regular one if CPU comes * online later on. Make sure every worker has * PF_THREAD_BOUND set. */ if (bind) kthread_bind(worker->task, gcwq->cpu); else worker->task->flags |= PF_THREAD_BOUND; return worker; fail: if (id >= 0) { spin_lock_irq(&gcwq->lock); ida_remove(&gcwq->worker_ida, id); spin_unlock_irq(&gcwq->lock); } kfree(worker); return NULL; } /** * start_worker - start a newly created worker * @worker: worker to start * * Make the gcwq aware of @worker and start it. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void start_worker(struct worker *worker) { worker->flags |= WORKER_STARTED; worker->gcwq->nr_workers++; worker_enter_idle(worker); wake_up_process(worker->task); } /** * destroy_worker - destroy a workqueue worker * @worker: worker to be destroyed * * Destroy @worker and adjust @gcwq stats accordingly. * * CONTEXT: * spin_lock_irq(gcwq->lock) which is released and regrabbed. */ static void destroy_worker(struct worker *worker) { struct global_cwq *gcwq = worker->gcwq; int id = worker->id; /* sanity check frenzy */ BUG_ON(worker->current_work); BUG_ON(!list_empty(&worker->scheduled)); if (worker->flags & WORKER_STARTED) gcwq->nr_workers--; if (worker->flags & WORKER_IDLE) gcwq->nr_idle--; list_del_init(&worker->entry); worker->flags |= WORKER_DIE; spin_unlock_irq(&gcwq->lock); kthread_stop(worker->task); kfree(worker); spin_lock_irq(&gcwq->lock); ida_remove(&gcwq->worker_ida, id); } /** * move_linked_works - move linked works to a list * @work: start of series of works to be scheduled * @head: target list to append @work to * @nextp: out paramter for nested worklist walking * * Schedule linked works starting from @work to @head. Work series to * be scheduled starts at @work and includes any consecutive work with * WORK_STRUCT_LINKED set in its predecessor. * * If @nextp is not NULL, it's updated to point to the next work of * the last scheduled work. This allows move_linked_works() to be * nested inside outer list_for_each_entry_safe(). * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void move_linked_works(struct work_struct *work, struct list_head *head, struct work_struct **nextp) { struct work_struct *n; /* * Linked worklist will always end before the end of the list, * use NULL for list head. */ list_for_each_entry_safe_from(work, n, NULL, entry) { list_move_tail(&work->entry, head); if (!(*work_data_bits(work) & WORK_STRUCT_LINKED)) break; } /* * If we're already inside safe list traversal and have moved * multiple works to the scheduled queue, the next position * needs to be updated. */ if (nextp) *nextp = n; } static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) { struct work_struct *work = list_first_entry(&cwq->delayed_works, struct work_struct, entry); move_linked_works(work, &cwq->worklist, NULL); cwq->nr_active++; } /** * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight * @cwq: cwq of interest * @color: color of work which left the queue * * A work either has completed or is removed from pending queue, * decrement nr_in_flight of its cwq and handle workqueue flushing. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color) { /* ignore uncolored works */ if (color == WORK_NO_COLOR) return; cwq->nr_in_flight[color]--; cwq->nr_active--; if (!list_empty(&cwq->delayed_works)) { /* one down, submit a delayed one */ if (cwq->nr_active < cwq->max_active) cwq_activate_first_delayed(cwq); } else if (!cwq->nr_active && cwq->wq->flags & WQ_SINGLE_CPU) { /* this was the last work, unbind from single cpu */ cwq_unbind_single_cpu(cwq); } /* is flush in progress and are we at the flushing tip? */ if (likely(cwq->flush_color != color)) return; /* are there still in-flight works? */ if (cwq->nr_in_flight[color]) return; /* this cwq is done, clear flush_color */ cwq->flush_color = -1; /* * If this was the last cwq, wake up the first flusher. It * will handle the rest. */ if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush)) complete(&cwq->wq->first_flusher->done); } /** * process_one_work - process single work * @worker: self * @work: work to process * * Process @work. This function contains all the logics necessary to * process a single work including synchronization against and * interaction with other workers on the same cpu, queueing and * flushing. As long as context requirement is met, any worker can * call this function to process a work. * * CONTEXT: * spin_lock_irq(gcwq->lock) which is released and regrabbed. */ static void process_one_work(struct worker *worker, struct work_struct *work) { struct cpu_workqueue_struct *cwq = worker->cwq; struct global_cwq *gcwq = cwq->gcwq; struct hlist_head *bwh = busy_worker_head(gcwq, work); work_func_t f = work->func; int work_color; #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 /* claim and process */ debug_work_deactivate(work); hlist_add_head(&worker->hentry, bwh); worker->current_work = work; worker->current_cwq = cwq; work_color = get_work_color(work); list_del_init(&work->entry); spin_unlock_irq(&gcwq->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(&gcwq->lock); /* we're done with it, release */ hlist_del_init(&worker->hentry); worker->current_work = NULL; worker->current_cwq = NULL; cwq_dec_nr_in_flight(cwq, work_color); } /** * process_scheduled_works - process scheduled works * @worker: self * * Process all scheduled works. Please note that the scheduled list * may change while processing a work, so this function repeatedly * fetches a work from the top and executes it. * * CONTEXT: * spin_lock_irq(gcwq->lock) which may be released and regrabbed * multiple times. */ static void process_scheduled_works(struct worker *worker) { while (!list_empty(&worker->scheduled)) { struct work_struct *work = list_first_entry(&worker->scheduled, struct work_struct, entry); process_one_work(worker, work); } } /** * worker_thread - the worker thread function * @__worker: self * * The cwq worker thread function. */ static int worker_thread(void *__worker) { struct worker *worker = __worker; struct global_cwq *gcwq = worker->gcwq; struct cpu_workqueue_struct *cwq = worker->cwq; woke_up: spin_lock_irq(&gcwq->lock); /* DIE can be set only while we're idle, checking here is enough */ if (worker->flags & WORKER_DIE) { spin_unlock_irq(&gcwq->lock); return 0; } worker_leave_idle(worker); recheck: /* * ->scheduled list can only be filled while a worker is * preparing to process a work or actually processing it. * Make sure nobody diddled with it while I was sleeping. */ BUG_ON(!list_empty(&worker->scheduled)); while (!list_empty(&cwq->worklist)) { struct work_struct *work = list_first_entry(&cwq->worklist, struct work_struct, entry); /* * The following is a rather inefficient way to close * race window against cpu hotplug operations. Will * be replaced soon. */ if (unlikely(!(worker->flags & WORKER_ROGUE) && !cpumask_equal(&worker->task->cpus_allowed, get_cpu_mask(gcwq->cpu)))) { spin_unlock_irq(&gcwq->lock); set_cpus_allowed_ptr(worker->task, get_cpu_mask(gcwq->cpu)); cpu_relax(); spin_lock_irq(&gcwq->lock); goto recheck; } if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) { /* optimization path, not strictly necessary */ process_one_work(worker, work); if (unlikely(!list_empty(&worker->scheduled))) process_scheduled_works(worker); } else { move_linked_works(work, &worker->scheduled, NULL); process_scheduled_works(worker); } } /* * gcwq->lock is held and there's no work to process, sleep. * Workers are woken up only while holding gcwq->lock, so * setting the current state before releasing gcwq->lock is * enough to prevent losing any event. */ worker_enter_idle(worker); __set_current_state(TASK_INTERRUPTIBLE); spin_unlock_irq(&gcwq->lock); schedule(); goto woke_up; } 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); } /** * insert_wq_barrier - insert a barrier work * @cwq: cwq to insert barrier into * @barr: wq_barrier to insert * @target: target work to attach @barr to * @worker: worker currently executing @target, NULL if @target is not executing * * @barr is linked to @target such that @barr is completed only after * @target finishes execution. Please note that the ordering * guarantee is observed only with respect to @target and on the local * cpu. * * Currently, a queued barrier can't be canceled. This is because * try_to_grab_pending() can't determine whether the work to be * grabbed is at the head of the queue and thus can't clear LINKED * flag of the previous work while there must be a valid next work * after a work with LINKED flag set. * * Note that when @worker is non-NULL, @target may be modified * underneath us, so we can't reliably determine cwq from @target. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void insert_wq_barrier(struct cpu_workqueue_struct *cwq, struct wq_barrier *barr, struct work_struct *target, struct worker *worker) { struct list_head *head; unsigned int linked = 0; /* * debugobject calls are safe here even with gcwq->lock locked * as we know for sure that this will not trigger any of the * checks and call back into the fixup functions where we * might deadlock. */ INIT_WORK_ON_STACK(&barr->work, wq_barrier_func); __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work)); init_completion(&barr->done); /* * If @target is currently being executed, schedule the * barrier to the worker; otherwise, put it after @target. */ if (worker) head = worker->scheduled.next; else { unsigned long *bits = work_data_bits(target); head = target->entry.next; /* there can already be other linked works, inherit and set */ linked = *bits & WORK_STRUCT_LINKED; __set_bit(WORK_STRUCT_LINKED_BIT, bits); } debug_work_activate(&barr->work); insert_work(cwq, &barr->work, head, work_color_to_flags(WORK_NO_COLOR) | linked); } /** * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing * @wq: workqueue being flushed * @flush_color: new flush color, < 0 for no-op * @work_color: new work color, < 0 for no-op * * Prepare cwqs for workqueue flushing. * * If @flush_color is non-negative, flush_color on all cwqs should be * -1. If no cwq has in-flight commands at the specified color, all * cwq->flush_color's stay at -1 and %false is returned. If any cwq * has in flight commands, its cwq->flush_color is set to * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq * wakeup logic is armed and %true is returned. * * The caller should have initialized @wq->first_flusher prior to * calling this function with non-negative @flush_color. If * @flush_color is negative, no flush color update is done and %false * is returned. * * If @work_color is non-negative, all cwqs should have the same * work_color which is previous to @work_color and all will be * advanced to @work_color. * * CONTEXT: * mutex_lock(wq->flush_mutex). * * RETURNS: * %true if @flush_color >= 0 and there's something to flush. %false * otherwise. */ static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq, int flush_color, int work_color) { bool wait = false; unsigned int cpu; if (flush_color >= 0) { BUG_ON(atomic_read(&wq->nr_cwqs_to_flush)); atomic_set(&wq->nr_cwqs_to_flush, 1); } for_each_possible_cpu(cpu) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); struct global_cwq *gcwq = cwq->gcwq; spin_lock_irq(&gcwq->lock); if (flush_color >= 0) { BUG_ON(cwq->flush_color != -1); if (cwq->nr_in_flight[flush_color]) { cwq->flush_color = flush_color; atomic_inc(&wq->nr_cwqs_to_flush); wait = true; } } if (work_color >= 0) { BUG_ON(work_color != work_next_color(cwq->work_color)); cwq->work_color = work_color; } spin_unlock_irq(&gcwq->lock); } if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush)) complete(&wq->first_flusher->done); return wait; } /** * 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. */ void flush_workqueue(struct workqueue_struct *wq) { struct wq_flusher this_flusher = { .list = LIST_HEAD_INIT(this_flusher.list), .flush_color = -1, .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done), }; int next_color; lock_map_acquire(&wq->lockdep_map); lock_map_release(&wq->lockdep_map); mutex_lock(&wq->flush_mutex); /* * Start-to-wait phase */ next_color = work_next_color(wq->work_color); if (next_color != wq->flush_color) { /* * Color space is not full. The current work_color * becomes our flush_color and work_color is advanced * by one. */ BUG_ON(!list_empty(&wq->flusher_overflow)); this_flusher.flush_color = wq->work_color; wq->work_color = next_color; if (!wq->first_flusher) { /* no flush in progress, become the first flusher */ BUG_ON(wq->flush_color != this_flusher.flush_color); wq->first_flusher = &this_flusher; if (!flush_workqueue_prep_cwqs(wq, wq->flush_color, wq->work_color)) { /* nothing to flush, done */ wq->flush_color = next_color; wq->first_flusher = NULL; goto out_unlock; } } else { /* wait in queue */ BUG_ON(wq->flush_color == this_flusher.flush_color); list_add_tail(&this_flusher.list, &wq->flusher_queue); flush_workqueue_prep_cwqs(wq, -1, wq->work_color); } } else { /* * Oops, color space is full, wait on overflow queue. * The next flush completion will assign us * flush_color and transfer to flusher_queue. */ list_add_tail(&this_flusher.list, &wq->flusher_overflow); } mutex_unlock(&wq->flush_mutex); wait_for_completion(&this_flusher.done); /* * Wake-up-and-cascade phase * * First flushers are responsible for cascading flushes and * handling overflow. Non-first flushers can simply return. */ if (wq->first_flusher != &this_flusher) return; mutex_lock(&wq->flush_mutex); wq->first_flusher = NULL; BUG_ON(!list_empty(&this_flusher.list)); BUG_ON(wq->flush_color != this_flusher.flush_color); while (true) { struct wq_flusher *next, *tmp; /* complete all the flushers sharing the current flush color */ list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) { if (next->flush_color != wq->flush_color) break; list_del_init(&next->list); complete(&next->done); } BUG_ON(!list_empty(&wq->flusher_overflow) && wq->flush_color != work_next_color(wq->work_color)); /* this flush_color is finished, advance by one */ wq->flush_color = work_next_color(wq->flush_color); /* one color has been freed, handle overflow queue */ if (!list_empty(&wq->flusher_overflow)) { /* * Assign the same color to all overflowed * flushers, advance work_color and append to * flusher_queue. This is the start-to-wait * phase for these overflowed flushers. */ list_for_each_entry(tmp, &wq->flusher_overflow, list) tmp->flush_color = wq->work_color; wq->work_color = work_next_color(wq->work_color); list_splice_tail_init(&wq->flusher_overflow, &wq->flusher_queue); flush_workqueue_prep_cwqs(wq, -1, wq->work_color); } if (list_empty(&wq->flusher_queue)) { BUG_ON(wq->flush_color != wq->work_color); break; } /* * Need to flush more colors. Make the next flusher * the new first flusher and arm cwqs. */ BUG_ON(wq->flush_color == wq->work_color); BUG_ON(wq->flush_color != next->flush_color); list_del_init(&next->list); wq->first_flusher = next; if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1)) break; /* * Meh... this color is already done, clear first * flusher and repeat cascading. */ wq->first_flusher = NULL; } out_unlock: mutex_unlock(&wq->flush_mutex); } 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 worker *worker = NULL; struct cpu_workqueue_struct *cwq; struct global_cwq *gcwq; struct wq_barrier barr; might_sleep(); cwq = get_wq_data(work); if (!cwq) return 0; gcwq = cwq->gcwq; lock_map_acquire(&cwq->wq->lockdep_map); lock_map_release(&cwq->wq->lockdep_map); spin_lock_irq(&gcwq->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 already_gone; } else { if (cwq->worker && cwq->worker->current_work == work) worker = cwq->worker; if (!worker) goto already_gone; } insert_wq_barrier(cwq, &barr, work, worker); spin_unlock_irq(&gcwq->lock); wait_for_completion(&barr.done); destroy_work_on_stack(&barr.work); return 1; already_gone: spin_unlock_irq(&gcwq->lock); return 0; } 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 global_cwq *gcwq; struct cpu_workqueue_struct *cwq; int ret = -1; if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, 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; gcwq = cwq->gcwq; spin_lock_irq(&gcwq->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)) { debug_work_deactivate(work); list_del_init(&work->entry); cwq_dec_nr_in_flight(cwq, get_work_color(work)); ret = 1; } } spin_unlock_irq(&gcwq->lock); return ret; } static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq, struct work_struct *work) { struct global_cwq *gcwq = cwq->gcwq; struct wq_barrier barr; struct worker *worker; spin_lock_irq(&gcwq->lock); worker = NULL; if (unlikely(cwq->worker && cwq->worker->current_work == work)) { worker = cwq->worker; insert_wq_barrier(cwq, &barr, work, worker); } spin_unlock_irq(&gcwq->lock); if (unlikely(worker)) { wait_for_completion(&barr.done); destroy_work_on_stack(&barr.work); } } static void wait_on_work(struct work_struct *work) { struct cpu_workqueue_struct *cwq; struct workqueue_struct *wq; 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; for_each_possible_cpu(cpu) wait_on_cpu_work(get_cwq(cpu, wq), 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)); clear_wq_data(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 * * Returns zero if @work was already on the kernel-global workqueue and * non-zero otherwise. * * This puts a job in the kernel-global workqueue if it was not already * queued and leaves it in the same position on the kernel-global * workqueue otherwise. */ 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); /** * flush_delayed_work - block until a dwork_struct's callback has terminated * @dwork: the delayed work which is to be flushed * * Any timeout is cancelled, and any pending work is run immediately. */ void flush_delayed_work(struct delayed_work *dwork) { if (del_timer_sync(&dwork->timer)) { __queue_work(get_cpu(), get_wq_data(&dwork->work)->wq, &dwork->work); put_cpu(); } flush_work(&dwork->work); } EXPORT_SYMBOL(flush_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; int orig = -1; struct work_struct *works; works = alloc_percpu(struct work_struct); if (!works) return -ENOMEM; get_online_cpus(); /* * When running in keventd don't schedule a work item on * itself. Can just call directly because the work queue is * already bound. This also is faster. */ if (current_is_keventd()) orig = raw_smp_processor_id(); for_each_online_cpu(cpu) { struct work_struct *work = per_cpu_ptr(works, cpu); INIT_WORK(work, func); if (cpu != orig) schedule_work_on(cpu, work); } if (orig >= 0) func(per_cpu_ptr(works, orig)); for_each_online_cpu(cpu) flush_work(per_cpu_ptr(works, cpu)); put_online_cpus(); free_percpu(works); return 0; } /** * flush_scheduled_work - ensure that any scheduled work has run to completion. * * Forces execution of the kernel-global workqueue and blocks until its * completion. * * Think twice before calling this function! It's very easy to get into * trouble if you don't take great care. Either of the following situations * will lead to deadlock: * * One of the work items currently on the workqueue needs to acquire * a lock held by your code or its caller. * * Your code is running in the context of a work routine. * * They will be detected by lockdep when they occur, but the first might not * occur very often. It depends on what work items are on the workqueue and * what locks they need, which you have no control over. * * In most situations flushing the entire workqueue is overkill; you merely * need to know that a particular work item isn't queued and isn't running. * In such cases you should use cancel_delayed_work_sync() or * cancel_work_sync() instead. */ 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 = get_cwq(cpu, keventd_wq); if (current == cwq->worker->task) ret = 1; return ret; } static struct cpu_workqueue_struct *alloc_cwqs(void) { /* * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS. * Make sure that the alignment isn't lower than that of * unsigned long long. */ const size_t size = sizeof(struct cpu_workqueue_struct); const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS, __alignof__(unsigned long long)); struct cpu_workqueue_struct *cwqs; #ifndef CONFIG_SMP void *ptr; /* * On UP, percpu allocator doesn't honor alignment parameter * and simply uses arch-dependent default. Allocate enough * room to align cwq and put an extra pointer at the end * pointing back to the originally allocated pointer which * will be used for free. * * FIXME: This really belongs to UP percpu code. Update UP * percpu code to honor alignment and remove this ugliness. */ ptr = __alloc_percpu(size + align + sizeof(void *), 1); cwqs = PTR_ALIGN(ptr, align); *(void **)per_cpu_ptr(cwqs + 1, 0) = ptr; #else /* On SMP, percpu allocator can do it itself */ cwqs = __alloc_percpu(size, align); #endif /* just in case, make sure it's actually aligned */ BUG_ON(!IS_ALIGNED((unsigned long)cwqs, align)); return cwqs; } static void free_cwqs(struct cpu_workqueue_struct *cwqs) { #ifndef CONFIG_SMP /* on UP, the pointer to free is stored right after the cwq */ if (cwqs) free_percpu(*(void **)per_cpu_ptr(cwqs + 1, 0)); #else free_percpu(cwqs); #endif } struct workqueue_struct *__create_workqueue_key(const char *name, unsigned int flags, int max_active, struct lock_class_key *key, const char *lock_name) { struct workqueue_struct *wq; bool failed = false; unsigned int cpu; max_active = clamp_val(max_active, 1, INT_MAX); wq = kzalloc(sizeof(*wq), GFP_KERNEL); if (!wq) goto err; wq->cpu_wq = alloc_cwqs(); if (!wq->cpu_wq) goto err; wq->flags = flags; wq->saved_max_active = max_active; mutex_init(&wq->flush_mutex); atomic_set(&wq->nr_cwqs_to_flush, 0); INIT_LIST_HEAD(&wq->flusher_queue); INIT_LIST_HEAD(&wq->flusher_overflow); wq->single_cpu = NR_CPUS; wq->name = name; lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); INIT_LIST_HEAD(&wq->list); cpu_maps_update_begin(); /* * 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) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); struct global_cwq *gcwq = get_gcwq(cpu); BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK); cwq->gcwq = gcwq; cwq->wq = wq; cwq->flush_color = -1; cwq->max_active = max_active; INIT_LIST_HEAD(&cwq->worklist); INIT_LIST_HEAD(&cwq->delayed_works); if (failed) continue; cwq->worker = create_worker(cwq, cpu_online(cpu)); if (cwq->worker) start_worker(cwq->worker); else failed = true; } /* * workqueue_lock protects global freeze state and workqueues * list. Grab it, set max_active accordingly and add the new * workqueue to workqueues list. */ spin_lock(&workqueue_lock); if (workqueue_freezing && wq->flags & WQ_FREEZEABLE) for_each_possible_cpu(cpu) get_cwq(cpu, wq)->max_active = 0; list_add(&wq->list, &workqueues); spin_unlock(&workqueue_lock); cpu_maps_update_done(); if (failed) { destroy_workqueue(wq); wq = NULL; } return wq; err: if (wq) { free_cwqs(wq->cpu_wq); kfree(wq); } return NULL; } EXPORT_SYMBOL_GPL(__create_workqueue_key); /** * 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) { unsigned int cpu; flush_workqueue(wq); /* * wq list is used to freeze wq, remove from list after * flushing is complete in case freeze races us. */ cpu_maps_update_begin(); spin_lock(&workqueue_lock); list_del(&wq->list); spin_unlock(&workqueue_lock); cpu_maps_update_done(); for_each_possible_cpu(cpu) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); int i; if (cwq->worker) { spin_lock_irq(&cwq->gcwq->lock); destroy_worker(cwq->worker); cwq->worker = NULL; spin_unlock_irq(&cwq->gcwq->lock); } for (i = 0; i < WORK_NR_COLORS; i++) BUG_ON(cwq->nr_in_flight[i]); BUG_ON(cwq->nr_active); BUG_ON(!list_empty(&cwq->delayed_works)); } free_cwqs(wq->cpu_wq); kfree(wq); } EXPORT_SYMBOL_GPL(destroy_workqueue); /* * CPU hotplug. * * CPU hotplug is implemented by allowing cwqs to be detached from * CPU, running with unbound workers and allowing them to be * reattached later if the cpu comes back online. A separate thread * is created to govern cwqs in such state and is called the trustee. * * Trustee states and their descriptions. * * START Command state used on startup. On CPU_DOWN_PREPARE, a * new trustee is started with this state. * * IN_CHARGE Once started, trustee will enter this state after * making all existing workers rogue. DOWN_PREPARE waits * for trustee to enter this state. After reaching * IN_CHARGE, trustee tries to execute the pending * worklist until it's empty and the state is set to * BUTCHER, or the state is set to RELEASE. * * BUTCHER Command state which is set by the cpu callback after * the cpu has went down. Once this state is set trustee * knows that there will be no new works on the worklist * and once the worklist is empty it can proceed to * killing idle workers. * * RELEASE Command state which is set by the cpu callback if the * cpu down has been canceled or it has come online * again. After recognizing this state, trustee stops * trying to drain or butcher and transits to DONE. * * DONE Trustee will enter this state after BUTCHER or RELEASE * is complete. * * trustee CPU draining * took over down complete * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE * | | ^ * | CPU is back online v return workers | * ----------------> RELEASE -------------- */ /** * trustee_wait_event_timeout - timed event wait for trustee * @cond: condition to wait for * @timeout: timeout in jiffies * * wait_event_timeout() for trustee to use. Handles locking and * checks for RELEASE request. * * CONTEXT: * spin_lock_irq(gcwq->lock) which may be released and regrabbed * multiple times. To be used by trustee. * * RETURNS: * Positive indicating left time if @cond is satisfied, 0 if timed * out, -1 if canceled. */ #define trustee_wait_event_timeout(cond, timeout) ({ \ long __ret = (timeout); \ while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \ __ret) { \ spin_unlock_irq(&gcwq->lock); \ __wait_event_timeout(gcwq->trustee_wait, (cond) || \ (gcwq->trustee_state == TRUSTEE_RELEASE), \ __ret); \ spin_lock_irq(&gcwq->lock); \ } \ gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \ }) /** * trustee_wait_event - event wait for trustee * @cond: condition to wait for * * wait_event() for trustee to use. Automatically handles locking and * checks for CANCEL request. * * CONTEXT: * spin_lock_irq(gcwq->lock) which may be released and regrabbed * multiple times. To be used by trustee. * * RETURNS: * 0 if @cond is satisfied, -1 if canceled. */ #define trustee_wait_event(cond) ({ \ long __ret1; \ __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\ __ret1 < 0 ? -1 : 0; \ }) static int __cpuinit trustee_thread(void *__gcwq) { struct global_cwq *gcwq = __gcwq; struct worker *worker; struct hlist_node *pos; int i; BUG_ON(gcwq->cpu != smp_processor_id()); spin_lock_irq(&gcwq->lock); /* * Make all workers rogue. Trustee must be bound to the * target cpu and can't be cancelled. */ BUG_ON(gcwq->cpu != smp_processor_id()); list_for_each_entry(worker, &gcwq->idle_list, entry) worker->flags |= WORKER_ROGUE; for_each_busy_worker(worker, i, pos, gcwq) worker->flags |= WORKER_ROGUE; /* * We're now in charge. Notify and proceed to drain. We need * to keep the gcwq running during the whole CPU down * procedure as other cpu hotunplug callbacks may need to * flush currently running tasks. */ gcwq->trustee_state = TRUSTEE_IN_CHARGE; wake_up_all(&gcwq->trustee_wait); /* * The original cpu is in the process of dying and may go away * anytime now. When that happens, we and all workers would * be migrated to other cpus. Try draining any left work. * Note that if the gcwq is frozen, there may be frozen works * in freezeable cwqs. Don't declare completion while frozen. */ while (gcwq->nr_workers != gcwq->nr_idle || gcwq->flags & GCWQ_FREEZING || gcwq->trustee_state == TRUSTEE_IN_CHARGE) { /* give a breather */ if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0) break; } /* notify completion */ gcwq->trustee = NULL; gcwq->trustee_state = TRUSTEE_DONE; wake_up_all(&gcwq->trustee_wait); spin_unlock_irq(&gcwq->lock); return 0; } /** * wait_trustee_state - wait for trustee to enter the specified state * @gcwq: gcwq the trustee of interest belongs to * @state: target state to wait for * * Wait for the trustee to reach @state. DONE is already matched. * * CONTEXT: * spin_lock_irq(gcwq->lock) which may be released and regrabbed * multiple times. To be used by cpu_callback. */ static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state) { if (!(gcwq->trustee_state == state || gcwq->trustee_state == TRUSTEE_DONE)) { spin_unlock_irq(&gcwq->lock); __wait_event(gcwq->trustee_wait, gcwq->trustee_state == state || gcwq->trustee_state == TRUSTEE_DONE); spin_lock_irq(&gcwq->lock); } } static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { unsigned int cpu = (unsigned long)hcpu; struct global_cwq *gcwq = get_gcwq(cpu); struct task_struct *new_trustee = NULL; struct worker *worker; struct hlist_node *pos; unsigned long flags; int i; action &= ~CPU_TASKS_FROZEN; switch (action) { case CPU_DOWN_PREPARE: new_trustee = kthread_create(trustee_thread, gcwq, "workqueue_trustee/%d\n", cpu); if (IS_ERR(new_trustee)) return notifier_from_errno(PTR_ERR(new_trustee)); kthread_bind(new_trustee, cpu); } /* some are called w/ irq disabled, don't disturb irq status */ spin_lock_irqsave(&gcwq->lock, flags); switch (action) { case CPU_DOWN_PREPARE: /* initialize trustee and tell it to acquire the gcwq */ BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE); gcwq->trustee = new_trustee; gcwq->trustee_state = TRUSTEE_START; wake_up_process(gcwq->trustee); wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE); break; case CPU_POST_DEAD: gcwq->trustee_state = TRUSTEE_BUTCHER; break; case CPU_DOWN_FAILED: case CPU_ONLINE: if (gcwq->trustee_state != TRUSTEE_DONE) { gcwq->trustee_state = TRUSTEE_RELEASE; wake_up_process(gcwq->trustee); wait_trustee_state(gcwq, TRUSTEE_DONE); } /* clear ROGUE from all workers */ list_for_each_entry(worker, &gcwq->idle_list, entry) worker->flags &= ~WORKER_ROGUE; for_each_busy_worker(worker, i, pos, gcwq) worker->flags &= ~WORKER_ROGUE; break; } spin_unlock_irqrestore(&gcwq->lock, flags); return notifier_from_errno(0); } #ifdef CONFIG_SMP struct work_for_cpu { struct completion completion; long (*fn)(void *); void *arg; long ret; }; static int do_work_for_cpu(void *_wfc) { struct work_for_cpu *wfc = _wfc; wfc->ret = wfc->fn(wfc->arg); complete(&wfc->completion); return 0; } /** * 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 the value @fn returns. * It is up to the caller to ensure that the cpu doesn't go offline. * The caller must not hold any locks which would prevent @fn from completing. */ long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) { struct task_struct *sub_thread; struct work_for_cpu wfc = { .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion), .fn = fn, .arg = arg, }; sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu"); if (IS_ERR(sub_thread)) return PTR_ERR(sub_thread); kthread_bind(sub_thread, cpu); wake_up_process(sub_thread); wait_for_completion(&wfc.completion); return wfc.ret; } EXPORT_SYMBOL_GPL(work_on_cpu); #endif /* CONFIG_SMP */ #ifdef CONFIG_FREEZER /** * freeze_workqueues_begin - begin freezing workqueues * * Start freezing workqueues. After this function returns, all * freezeable workqueues will queue new works to their frozen_works * list instead of the cwq ones. * * CONTEXT: * Grabs and releases workqueue_lock and gcwq->lock's. */ void freeze_workqueues_begin(void) { struct workqueue_struct *wq; unsigned int cpu; spin_lock(&workqueue_lock); BUG_ON(workqueue_freezing); workqueue_freezing = true; for_each_possible_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); spin_lock_irq(&gcwq->lock); BUG_ON(gcwq->flags & GCWQ_FREEZING); gcwq->flags |= GCWQ_FREEZING; list_for_each_entry(wq, &workqueues, list) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); if (wq->flags & WQ_FREEZEABLE) cwq->max_active = 0; } spin_unlock_irq(&gcwq->lock); } spin_unlock(&workqueue_lock); } /** * freeze_workqueues_busy - are freezeable workqueues still busy? * * Check whether freezing is complete. This function must be called * between freeze_workqueues_begin() and thaw_workqueues(). * * CONTEXT: * Grabs and releases workqueue_lock. * * RETURNS: * %true if some freezeable workqueues are still busy. %false if * freezing is complete. */ bool freeze_workqueues_busy(void) { struct workqueue_struct *wq; unsigned int cpu; bool busy = false; spin_lock(&workqueue_lock); BUG_ON(!workqueue_freezing); for_each_possible_cpu(cpu) { /* * nr_active is monotonically decreasing. It's safe * to peek without lock. */ list_for_each_entry(wq, &workqueues, list) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); if (!(wq->flags & WQ_FREEZEABLE)) continue; BUG_ON(cwq->nr_active < 0); if (cwq->nr_active) { busy = true; goto out_unlock; } } } out_unlock: spin_unlock(&workqueue_lock); return busy; } /** * thaw_workqueues - thaw workqueues * * Thaw workqueues. Normal queueing is restored and all collected * frozen works are transferred to their respective cwq worklists. * * CONTEXT: * Grabs and releases workqueue_lock and gcwq->lock's. */ void thaw_workqueues(void) { struct workqueue_struct *wq; unsigned int cpu; spin_lock(&workqueue_lock); if (!workqueue_freezing) goto out_unlock; for_each_possible_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); spin_lock_irq(&gcwq->lock); BUG_ON(!(gcwq->flags & GCWQ_FREEZING)); gcwq->flags &= ~GCWQ_FREEZING; list_for_each_entry(wq, &workqueues, list) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); if (!(wq->flags & WQ_FREEZEABLE)) continue; /* restore max_active and repopulate worklist */ cwq->max_active = wq->saved_max_active; while (!list_empty(&cwq->delayed_works) && cwq->nr_active < cwq->max_active) cwq_activate_first_delayed(cwq); /* perform delayed unbind from single cpu if empty */ if (wq->single_cpu == gcwq->cpu && !cwq->nr_active && list_empty(&cwq->delayed_works)) cwq_unbind_single_cpu(cwq); wake_up_process(cwq->worker->task); } spin_unlock_irq(&gcwq->lock); } workqueue_freezing = false; out_unlock: spin_unlock(&workqueue_lock); } #endif /* CONFIG_FREEZER */ void __init init_workqueues(void) { unsigned int cpu; int i; hotcpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE); /* initialize gcwqs */ for_each_possible_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); spin_lock_init(&gcwq->lock); gcwq->cpu = cpu; INIT_LIST_HEAD(&gcwq->idle_list); for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) INIT_HLIST_HEAD(&gcwq->busy_hash[i]); ida_init(&gcwq->worker_ida); gcwq->trustee_state = TRUSTEE_DONE; init_waitqueue_head(&gcwq->trustee_wait); } keventd_wq = create_workqueue("events"); BUG_ON(!keventd_wq); }