/* * kernel/workqueue.c - generic async execution with shared worker pool * * Copyright (C) 2002 Ingo Molnar * * Derived from the taskqueue/keventd code by: * David Woodhouse * Andrew Morton * Kai Petzke * Theodore Ts'o * * Made to use alloc_percpu by Christoph Lameter. * * Copyright (C) 2010 SUSE Linux Products GmbH * Copyright (C) 2010 Tejun Heo * * This is the generic async execution mechanism. Work items as are * executed in process context. The worker pool is shared and * automatically managed. There is one worker pool for each CPU and * one extra for works which are better served by workers which are * not bound to any specific CPU. * * Please read Documentation/workqueue.txt for details. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "workqueue_sched.h" enum { /* global_cwq flags */ GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */ GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */ GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */ GCWQ_FREEZING = 1 << 3, /* freeze in progress */ GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */ /* worker flags */ WORKER_STARTED = 1 << 0, /* started */ WORKER_DIE = 1 << 1, /* die die die */ WORKER_IDLE = 1 << 2, /* is idle */ WORKER_PREP = 1 << 3, /* preparing to run works */ WORKER_ROGUE = 1 << 4, /* not bound to any cpu */ WORKER_REBIND = 1 << 5, /* mom is home, come back */ WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */ WORKER_UNBOUND = 1 << 7, /* worker is unbound */ WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND | WORKER_CPU_INTENSIVE | WORKER_UNBOUND, /* 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, MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */ IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */ MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2, /* call for help after 10ms (min two ticks) */ MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */ CREATE_COOLDOWN = HZ, /* time to breath after fail */ TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */ /* * Rescue workers are used only on emergencies and shared by * all cpus. Give -20. */ RESCUER_NICE_LEVEL = -20, }; /* * Structure fields follow one of the following exclusion rules. * * I: Modifiable by initialization/destruction paths and read-only for * everyone else. * * P: Preemption protected. Disabling preemption is enough and should * only be modified and accessed from the local cpu. * * L: gcwq->lock protected. Access with gcwq->lock held. * * X: During normal operation, modification requires gcwq->lock and * should be done only from local cpu. Either disabling preemption * on local cpu or grabbing gcwq->lock is enough for read access. * If GCWQ_DISASSOCIATED is set, it's identical to L. * * F: wq->flush_mutex protected. * * W: workqueue_lock protected. */ struct global_cwq; /* * The poor guys doing the actual heavy lifting. All on-duty workers * are either serving the manager role, on idle list or on busy hash. */ 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 */ /* 64 bytes boundary on 64bit, 32 on 32bit */ unsigned long last_active; /* L: last active timestamp */ unsigned int flags; /* X: flags */ int id; /* I: worker id */ struct work_struct rebind_work; /* L: rebind worker to cpu */ }; /* * Global per-cpu workqueue. There's one and only one for each cpu * and all works are queued and processed here regardless of their * target workqueues. */ struct global_cwq { spinlock_t lock; /* the gcwq lock */ struct list_head worklist; /* L: list of pending works */ 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; /* X: list of idle workers */ struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE]; /* L: hash of busy workers */ struct timer_list idle_timer; /* L: worker idle timeout */ struct timer_list mayday_timer; /* L: SOS timer for dworkers */ 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 */ struct worker *first_idle; /* L: first idle worker */ } ____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 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 */ }; /* * All cpumasks are assumed to be always set on UP and thus can't be * used to determine whether there's something to be done. */ #ifdef CONFIG_SMP typedef cpumask_var_t mayday_mask_t; #define mayday_test_and_set_cpu(cpu, mask) \ cpumask_test_and_set_cpu((cpu), (mask)) #define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask)) #define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask)) #define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp)) #define free_mayday_mask(mask) free_cpumask_var((mask)) #else typedef unsigned long mayday_mask_t; #define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask)) #define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask)) #define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask)) #define alloc_mayday_mask(maskp, gfp) true #define free_mayday_mask(mask) do { } while (0) #endif /* * The externally visible workqueue abstraction is an array of * per-CPU workqueues: */ struct workqueue_struct { unsigned int flags; /* W: WQ_* flags */ union { struct cpu_workqueue_struct __percpu *pcpu; struct cpu_workqueue_struct *single; unsigned long v; } 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 */ mayday_mask_t mayday_mask; /* cpus requesting rescue */ struct worker *rescuer; /* I: rescue worker */ int nr_drainers; /* W: drain in progress */ int saved_max_active; /* W: saved cwq max_active */ const char *name; /* I: workqueue name */ #ifdef CONFIG_LOCKDEP struct lockdep_map lockdep_map; #endif }; struct workqueue_struct *system_wq __read_mostly; struct workqueue_struct *system_long_wq __read_mostly; struct workqueue_struct *system_nrt_wq __read_mostly; struct workqueue_struct *system_unbound_wq __read_mostly; struct workqueue_struct *system_freezable_wq __read_mostly; EXPORT_SYMBOL_GPL(system_wq); EXPORT_SYMBOL_GPL(system_long_wq); EXPORT_SYMBOL_GPL(system_nrt_wq); EXPORT_SYMBOL_GPL(system_unbound_wq); EXPORT_SYMBOL_GPL(system_freezable_wq); #define CREATE_TRACE_POINTS #include #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) static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask, unsigned int sw) { if (cpu < nr_cpu_ids) { if (sw & 1) { cpu = cpumask_next(cpu, mask); if (cpu < nr_cpu_ids) return cpu; } if (sw & 2) return WORK_CPU_UNBOUND; } return WORK_CPU_NONE; } static inline int __next_wq_cpu(int cpu, const struct cpumask *mask, struct workqueue_struct *wq) { return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2); } /* * CPU iterators * * An extra gcwq is defined for an invalid cpu number * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any * specific CPU. The following iterators are similar to * for_each_*_cpu() iterators but also considers the unbound gcwq. * * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND * for_each_cwq_cpu() : possible CPUs for bound workqueues, * WORK_CPU_UNBOUND for unbound workqueues */ #define for_each_gcwq_cpu(cpu) \ for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \ (cpu) < WORK_CPU_NONE; \ (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3)) #define for_each_online_gcwq_cpu(cpu) \ for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \ (cpu) < WORK_CPU_NONE; \ (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3)) #define for_each_cwq_cpu(cpu, wq) \ for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \ (cpu) < WORK_CPU_NONE; \ (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq))) #ifdef CONFIG_DEBUG_OBJECTS_WORK static struct debug_obj_descr work_debug_descr; static void *work_debug_hint(void *addr) { return ((struct work_struct *) addr)->func; } /* * 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", .debug_hint = work_debug_hint, .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? */ /* * The almighty global cpu workqueues. nr_running is the only field * which is expected to be used frequently by other cpus via * try_to_wake_up(). Put it in a separate cacheline. */ static DEFINE_PER_CPU(struct global_cwq, global_cwq); static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running); /* * Global cpu workqueue and nr_running counter for unbound gcwq. The * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its * workers have WORKER_UNBOUND set. */ static struct global_cwq unbound_global_cwq; static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */ static int worker_thread(void *__worker); static struct global_cwq *get_gcwq(unsigned int cpu) { if (cpu != WORK_CPU_UNBOUND) return &per_cpu(global_cwq, cpu); else return &unbound_global_cwq; } static atomic_t *get_gcwq_nr_running(unsigned int cpu) { if (cpu != WORK_CPU_UNBOUND) return &per_cpu(gcwq_nr_running, cpu); else return &unbound_gcwq_nr_running; } static struct cpu_workqueue_struct *get_cwq(unsigned int cpu, struct workqueue_struct *wq) { if (!(wq->flags & WQ_UNBOUND)) { if (likely(cpu < nr_cpu_ids)) { #ifdef CONFIG_SMP return per_cpu_ptr(wq->cpu_wq.pcpu, cpu); #else return wq->cpu_wq.single; #endif } } else if (likely(cpu == WORK_CPU_UNBOUND)) return wq->cpu_wq.single; return NULL; } 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; } /* * A work's data points to the cwq with WORK_STRUCT_CWQ set while the * work is on queue. Once execution starts, WORK_STRUCT_CWQ is * cleared and the work data contains the cpu number it was last on. * * set_work_{cwq|cpu}() and clear_work_data() can be used to set the * cwq, cpu or clear work->data. These functions should only be * called while the work is owned - ie. while the PENDING bit is set. * * get_work_[g]cwq() can be used to obtain the gcwq or cwq * corresponding to a work. gcwq is available once the work has been * queued anywhere after initialization. cwq is available only from * queueing until execution starts. */ static inline void set_work_data(struct work_struct *work, unsigned long data, unsigned long flags) { BUG_ON(!work_pending(work)); atomic_long_set(&work->data, data | flags | work_static(work)); } static void set_work_cwq(struct work_struct *work, struct cpu_workqueue_struct *cwq, unsigned long extra_flags) { set_work_data(work, (unsigned long)cwq, WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags); } static void set_work_cpu(struct work_struct *work, unsigned int cpu) { set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING); } static void clear_work_data(struct work_struct *work) { set_work_data(work, WORK_STRUCT_NO_CPU, 0); } static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work) { unsigned long data = atomic_long_read(&work->data); if (data & WORK_STRUCT_CWQ) return (void *)(data & WORK_STRUCT_WQ_DATA_MASK); else return NULL; } static struct global_cwq *get_work_gcwq(struct work_struct *work) { unsigned long data = atomic_long_read(&work->data); unsigned int cpu; if (data & WORK_STRUCT_CWQ) return ((struct cpu_workqueue_struct *) (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq; cpu = data >> WORK_STRUCT_FLAG_BITS; if (cpu == WORK_CPU_NONE) return NULL; BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND); return get_gcwq(cpu); } /* * Policy functions. These define the policies on how the global * worker pool is managed. Unless noted otherwise, these functions * assume that they're being called with gcwq->lock held. */ static bool __need_more_worker(struct global_cwq *gcwq) { return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) || gcwq->flags & GCWQ_HIGHPRI_PENDING; } /* * Need to wake up a worker? Called from anything but currently * running workers. */ static bool need_more_worker(struct global_cwq *gcwq) { return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq); } /* Can I start working? Called from busy but !running workers. */ static bool may_start_working(struct global_cwq *gcwq) { return gcwq->nr_idle; } /* Do I need to keep working? Called from currently running workers. */ static bool keep_working(struct global_cwq *gcwq) { atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu); return !list_empty(&gcwq->worklist) && (atomic_read(nr_running) <= 1 || gcwq->flags & GCWQ_HIGHPRI_PENDING); } /* Do we need a new worker? Called from manager. */ static bool need_to_create_worker(struct global_cwq *gcwq) { return need_more_worker(gcwq) && !may_start_working(gcwq); } /* Do I need to be the manager? */ static bool need_to_manage_workers(struct global_cwq *gcwq) { return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS; } /* Do we have too many workers and should some go away? */ static bool too_many_workers(struct global_cwq *gcwq) { bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS; int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */ int nr_busy = gcwq->nr_workers - nr_idle; return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy; } /* * Wake up functions. */ /* Return the first worker. Safe with preemption disabled */ static struct worker *first_worker(struct global_cwq *gcwq) { if (unlikely(list_empty(&gcwq->idle_list))) return NULL; return list_first_entry(&gcwq->idle_list, struct worker, entry); } /** * wake_up_worker - wake up an idle worker * @gcwq: gcwq to wake worker for * * Wake up the first idle worker of @gcwq. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void wake_up_worker(struct global_cwq *gcwq) { struct worker *worker = first_worker(gcwq); if (likely(worker)) wake_up_process(worker->task); } /** * wq_worker_waking_up - a worker is waking up * @task: task waking up * @cpu: CPU @task is waking up to * * This function is called during try_to_wake_up() when a worker is * being awoken. * * CONTEXT: * spin_lock_irq(rq->lock) */ void wq_worker_waking_up(struct task_struct *task, unsigned int cpu) { struct worker *worker = kthread_data(task); if (!(worker->flags & WORKER_NOT_RUNNING)) atomic_inc(get_gcwq_nr_running(cpu)); } /** * wq_worker_sleeping - a worker is going to sleep * @task: task going to sleep * @cpu: CPU in question, must be the current CPU number * * This function is called during schedule() when a busy worker is * going to sleep. Worker on the same cpu can be woken up by * returning pointer to its task. * * CONTEXT: * spin_lock_irq(rq->lock) * * RETURNS: * Worker task on @cpu to wake up, %NULL if none. */ struct task_struct *wq_worker_sleeping(struct task_struct *task, unsigned int cpu) { struct worker *worker = kthread_data(task), *to_wakeup = NULL; struct global_cwq *gcwq = get_gcwq(cpu); atomic_t *nr_running = get_gcwq_nr_running(cpu); if (worker->flags & WORKER_NOT_RUNNING) return NULL; /* this can only happen on the local cpu */ BUG_ON(cpu != raw_smp_processor_id()); /* * The counterpart of the following dec_and_test, implied mb, * worklist not empty test sequence is in insert_work(). * Please read comment there. * * NOT_RUNNING is clear. This means that trustee is not in * charge and we're running on the local cpu w/ rq lock held * and preemption disabled, which in turn means that none else * could be manipulating idle_list, so dereferencing idle_list * without gcwq lock is safe. */ if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist)) to_wakeup = first_worker(gcwq); return to_wakeup ? to_wakeup->task : NULL; } /** * worker_set_flags - set worker flags and adjust nr_running accordingly * @worker: self * @flags: flags to set * @wakeup: wakeup an idle worker if necessary * * Set @flags in @worker->flags and adjust nr_running accordingly. If * nr_running becomes zero and @wakeup is %true, an idle worker is * woken up. * * CONTEXT: * spin_lock_irq(gcwq->lock) */ static inline void worker_set_flags(struct worker *worker, unsigned int flags, bool wakeup) { struct global_cwq *gcwq = worker->gcwq; WARN_ON_ONCE(worker->task != current); /* * If transitioning into NOT_RUNNING, adjust nr_running and * wake up an idle worker as necessary if requested by * @wakeup. */ if ((flags & WORKER_NOT_RUNNING) && !(worker->flags & WORKER_NOT_RUNNING)) { atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu); if (wakeup) { if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist)) wake_up_worker(gcwq); } else atomic_dec(nr_running); } worker->flags |= flags; } /** * worker_clr_flags - clear worker flags and adjust nr_running accordingly * @worker: self * @flags: flags to clear * * Clear @flags in @worker->flags and adjust nr_running accordingly. * * CONTEXT: * spin_lock_irq(gcwq->lock) */ static inline void worker_clr_flags(struct worker *worker, unsigned int flags) { struct global_cwq *gcwq = worker->gcwq; unsigned int oflags = worker->flags; WARN_ON_ONCE(worker->task != current); worker->flags &= ~flags; /* * If transitioning out of NOT_RUNNING, increment nr_running. Note * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask * of multiple flags, not a single flag. */ if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING)) if (!(worker->flags & WORKER_NOT_RUNNING)) atomic_inc(get_gcwq_nr_running(gcwq->cpu)); } /** * 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); } /** * gcwq_determine_ins_pos - find insertion position * @gcwq: gcwq of interest * @cwq: cwq a work is being queued for * * A work for @cwq is about to be queued on @gcwq, determine insertion * position for the work. If @cwq is for HIGHPRI wq, the work is * queued at the head of the queue but in FIFO order with respect to * other HIGHPRI works; otherwise, at the end of the queue. This * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that * there are HIGHPRI works pending. * * CONTEXT: * spin_lock_irq(gcwq->lock). * * RETURNS: * Pointer to inserstion position. */ static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq, struct cpu_workqueue_struct *cwq) { struct work_struct *twork; if (likely(!(cwq->wq->flags & WQ_HIGHPRI))) return &gcwq->worklist; list_for_each_entry(twork, &gcwq->worklist, entry) { struct cpu_workqueue_struct *tcwq = get_work_cwq(twork); if (!(tcwq->wq->flags & WQ_HIGHPRI)) break; } gcwq->flags |= GCWQ_HIGHPRI_PENDING; return &twork->entry; } /** * insert_work - insert a work into gcwq * @cwq: cwq @work belongs to * @work: work to insert * @head: insertion point * @extra_flags: extra WORK_STRUCT_* flags to set * * Insert @work which belongs to @cwq into @gcwq after @head. * @extra_flags is or'd to work_struct flags. * * 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) { struct global_cwq *gcwq = cwq->gcwq; /* we own @work, set data and link */ set_work_cwq(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); /* * Ensure either worker_sched_deactivated() sees the above * list_add_tail() or we see zero nr_running to avoid workers * lying around lazily while there are works to be processed. */ smp_mb(); if (__need_more_worker(gcwq)) wake_up_worker(gcwq); } /* * Test whether @work is being queued from another work executing on the * same workqueue. This is rather expensive and should only be used from * cold paths. */ static bool is_chained_work(struct workqueue_struct *wq) { unsigned long flags; unsigned int cpu; for_each_gcwq_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); struct worker *worker; struct hlist_node *pos; int i; spin_lock_irqsave(&gcwq->lock, flags); for_each_busy_worker(worker, i, pos, gcwq) { if (worker->task != current) continue; spin_unlock_irqrestore(&gcwq->lock, flags); /* * I'm @worker, no locking necessary. See if @work * is headed to the same workqueue. */ return worker->current_cwq->wq == wq; } spin_unlock_irqrestore(&gcwq->lock, flags); } return false; } 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 int work_flags; unsigned long flags; debug_work_activate(work); /* if dying, only works from the same workqueue are allowed */ if (unlikely(wq->flags & WQ_DRAINING) && WARN_ON_ONCE(!is_chained_work(wq))) return; /* determine gcwq to use */ if (!(wq->flags & WQ_UNBOUND)) { struct global_cwq *last_gcwq; if (unlikely(cpu == WORK_CPU_UNBOUND)) cpu = raw_smp_processor_id(); /* * It's multi cpu. If @wq is non-reentrant and @work * was previously on a different cpu, it might still * be running there, in which case the work needs to * be queued on that cpu to guarantee non-reentrance. */ gcwq = get_gcwq(cpu); if (wq->flags & WQ_NON_REENTRANT && (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) { struct worker *worker; spin_lock_irqsave(&last_gcwq->lock, flags); worker = find_worker_executing_work(last_gcwq, work); if (worker && worker->current_cwq->wq == wq) gcwq = last_gcwq; else { /* meh... not running there, queue here */ spin_unlock_irqrestore(&last_gcwq->lock, flags); spin_lock_irqsave(&gcwq->lock, flags); } } else spin_lock_irqsave(&gcwq->lock, flags); } else { gcwq = get_gcwq(WORK_CPU_UNBOUND); spin_lock_irqsave(&gcwq->lock, flags); } /* gcwq determined, get cwq and queue */ cwq = get_cwq(gcwq->cpu, wq); trace_workqueue_queue_work(cpu, cwq, work); BUG_ON(!list_empty(&work->entry)); cwq->nr_in_flight[cwq->work_color]++; work_flags = work_color_to_flags(cwq->work_color); if (likely(cwq->nr_active < cwq->max_active)) { trace_workqueue_activate_work(work); cwq->nr_active++; worklist = gcwq_determine_ins_pos(gcwq, cwq); } else { work_flags |= WORK_STRUCT_DELAYED; worklist = &cwq->delayed_works; } insert_work(cwq, work, worklist, work_flags); 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_work_cwq(&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))) { unsigned int lcpu; 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. * Note that the work's gcwq is preserved to allow * reentrance detection for delayed works. */ if (!(wq->flags & WQ_UNBOUND)) { struct global_cwq *gcwq = get_work_gcwq(work); if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND) lcpu = gcwq->cpu; else lcpu = raw_smp_processor_id(); } else lcpu = WORK_CPU_UNBOUND; set_work_cwq(work, get_cwq(lcpu, 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)); /* can't use worker_set_flags(), also called from start_worker() */ worker->flags |= WORKER_IDLE; gcwq->nr_idle++; worker->last_active = jiffies; /* idle_list is LIFO */ list_add(&worker->entry, &gcwq->idle_list); if (likely(!(worker->flags & WORKER_ROGUE))) { if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer)) mod_timer(&gcwq->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); } else wake_up_all(&gcwq->trustee_wait); /* sanity check nr_running */ WARN_ON_ONCE(gcwq->nr_workers == gcwq->nr_idle && atomic_read(get_gcwq_nr_running(gcwq->cpu))); } /** * 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_clr_flags(worker, WORKER_IDLE); gcwq->nr_idle--; list_del_init(&worker->entry); } /** * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq * @worker: self * * Works which are scheduled while the cpu is online must at least be * scheduled to a worker which is bound to the cpu so that if they are * flushed from cpu callbacks while cpu is going down, they are * guaranteed to execute on the cpu. * * This function is to be used by rogue workers and rescuers to bind * themselves to the target cpu and may race with cpu going down or * coming online. kthread_bind() can't be used because it may put the * worker to already dead cpu and set_cpus_allowed_ptr() can't be used * verbatim as it's best effort and blocking and gcwq may be * [dis]associated in the meantime. * * This function tries set_cpus_allowed() and locks gcwq and verifies * the binding against GCWQ_DISASSOCIATED which is set during * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters * idle state or fetches works without dropping lock, it can guarantee * the scheduling requirement described in the first paragraph. * * CONTEXT: * Might sleep. Called without any lock but returns with gcwq->lock * held. * * RETURNS: * %true if the associated gcwq is online (@worker is successfully * bound), %false if offline. */ static bool worker_maybe_bind_and_lock(struct worker *worker) __acquires(&gcwq->lock) { struct global_cwq *gcwq = worker->gcwq; struct task_struct *task = worker->task; while (true) { /* * The following call may fail, succeed or succeed * without actually migrating the task to the cpu if * it races with cpu hotunplug operation. Verify * against GCWQ_DISASSOCIATED. */ if (!(gcwq->flags & GCWQ_DISASSOCIATED)) set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu)); spin_lock_irq(&gcwq->lock); if (gcwq->flags & GCWQ_DISASSOCIATED) return false; if (task_cpu(task) == gcwq->cpu && cpumask_equal(¤t->cpus_allowed, get_cpu_mask(gcwq->cpu))) return true; spin_unlock_irq(&gcwq->lock); /* * We've raced with CPU hot[un]plug. Give it a breather * and retry migration. cond_resched() is required here; * otherwise, we might deadlock against cpu_stop trying to * bring down the CPU on non-preemptive kernel. */ cpu_relax(); cond_resched(); } } /* * Function for worker->rebind_work used to rebind rogue busy workers * to the associated cpu which is coming back online. This is * scheduled by cpu up but can race with other cpu hotplug operations * and may be executed twice without intervening cpu down. */ static void worker_rebind_fn(struct work_struct *work) { struct worker *worker = container_of(work, struct worker, rebind_work); struct global_cwq *gcwq = worker->gcwq; if (worker_maybe_bind_and_lock(worker)) worker_clr_flags(worker, WORKER_REBIND); spin_unlock_irq(&gcwq->lock); } 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); INIT_WORK(&worker->rebind_work, worker_rebind_fn); /* on creation a worker is in !idle && prep state */ worker->flags = WORKER_PREP; } return worker; } /** * create_worker - create a new workqueue worker * @gcwq: gcwq the new worker will belong to * @bind: whether to set affinity to @cpu or not * * Create a new worker which is bound to @gcwq. 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 global_cwq *gcwq, bool bind) { bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND; struct worker *worker = NULL; int id = -1; 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->id = id; if (!on_unbound_cpu) worker->task = kthread_create_on_node(worker_thread, worker, cpu_to_node(gcwq->cpu), "kworker/%u:%d", gcwq->cpu, id); else worker->task = kthread_create(worker_thread, worker, "kworker/u:%d", 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 && !on_unbound_cpu) kthread_bind(worker->task, gcwq->cpu); else { worker->task->flags |= PF_THREAD_BOUND; if (on_unbound_cpu) worker->flags |= WORKER_UNBOUND; } 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); } static void idle_worker_timeout(unsigned long __gcwq) { struct global_cwq *gcwq = (void *)__gcwq; spin_lock_irq(&gcwq->lock); if (too_many_workers(gcwq)) { struct worker *worker; unsigned long expires; /* idle_list is kept in LIFO order, check the last one */ worker = list_entry(gcwq->idle_list.prev, struct worker, entry); expires = worker->last_active + IDLE_WORKER_TIMEOUT; if (time_before(jiffies, expires)) mod_timer(&gcwq->idle_timer, expires); else { /* it's been idle for too long, wake up manager */ gcwq->flags |= GCWQ_MANAGE_WORKERS; wake_up_worker(gcwq); } } spin_unlock_irq(&gcwq->lock); } static bool send_mayday(struct work_struct *work) { struct cpu_workqueue_struct *cwq = get_work_cwq(work); struct workqueue_struct *wq = cwq->wq; unsigned int cpu; if (!(wq->flags & WQ_RESCUER)) return false; /* mayday mayday mayday */ cpu = cwq->gcwq->cpu; /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */ if (cpu == WORK_CPU_UNBOUND) cpu = 0; if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask)) wake_up_process(wq->rescuer->task); return true; } static void gcwq_mayday_timeout(unsigned long __gcwq) { struct global_cwq *gcwq = (void *)__gcwq; struct work_struct *work; spin_lock_irq(&gcwq->lock); if (need_to_create_worker(gcwq)) { /* * We've been trying to create a new worker but * haven't been successful. We might be hitting an * allocation deadlock. Send distress signals to * rescuers. */ list_for_each_entry(work, &gcwq->worklist, entry) send_mayday(work); } spin_unlock_irq(&gcwq->lock); mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL); } /** * maybe_create_worker - create a new worker if necessary * @gcwq: gcwq to create a new worker for * * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to * have at least one idle worker on return from this function. If * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is * sent to all rescuers with works scheduled on @gcwq to resolve * possible allocation deadlock. * * On return, need_to_create_worker() is guaranteed to be false and * may_start_working() true. * * LOCKING: * spin_lock_irq(gcwq->lock) which may be released and regrabbed * multiple times. Does GFP_KERNEL allocations. Called only from * manager. * * RETURNS: * false if no action was taken and gcwq->lock stayed locked, true * otherwise. */ static bool maybe_create_worker(struct global_cwq *gcwq) __releases(&gcwq->lock) __acquires(&gcwq->lock) { if (!need_to_create_worker(gcwq)) return false; restart: spin_unlock_irq(&gcwq->lock); /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */ mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT); while (true) { struct worker *worker; worker = create_worker(gcwq, true); if (worker) { del_timer_sync(&gcwq->mayday_timer); spin_lock_irq(&gcwq->lock); start_worker(worker); BUG_ON(need_to_create_worker(gcwq)); return true; } if (!need_to_create_worker(gcwq)) break; __set_current_state(TASK_INTERRUPTIBLE); schedule_timeout(CREATE_COOLDOWN); if (!need_to_create_worker(gcwq)) break; } del_timer_sync(&gcwq->mayday_timer); spin_lock_irq(&gcwq->lock); if (need_to_create_worker(gcwq)) goto restart; return true; } /** * maybe_destroy_worker - destroy workers which have been idle for a while * @gcwq: gcwq to destroy workers for * * Destroy @gcwq workers which have been idle for longer than * IDLE_WORKER_TIMEOUT. * * LOCKING: * spin_lock_irq(gcwq->lock) which may be released and regrabbed * multiple times. Called only from manager. * * RETURNS: * false if no action was taken and gcwq->lock stayed locked, true * otherwise. */ static bool maybe_destroy_workers(struct global_cwq *gcwq) { bool ret = false; while (too_many_workers(gcwq)) { struct worker *worker; unsigned long expires; worker = list_entry(gcwq->idle_list.prev, struct worker, entry); expires = worker->last_active + IDLE_WORKER_TIMEOUT; if (time_before(jiffies, expires)) { mod_timer(&gcwq->idle_timer, expires); break; } destroy_worker(worker); ret = true; } return ret; } /** * manage_workers - manage worker pool * @worker: self * * Assume the manager role and manage gcwq worker pool @worker belongs * to. At any given time, there can be only zero or one manager per * gcwq. The exclusion is handled automatically by this function. * * The caller can safely start processing works on false return. On * true return, it's guaranteed that need_to_create_worker() is false * and may_start_working() is true. * * CONTEXT: * spin_lock_irq(gcwq->lock) which may be released and regrabbed * multiple times. Does GFP_KERNEL allocations. * * RETURNS: * false if no action was taken and gcwq->lock stayed locked, true if * some action was taken. */ static bool manage_workers(struct worker *worker) { struct global_cwq *gcwq = worker->gcwq; bool ret = false; if (gcwq->flags & GCWQ_MANAGING_WORKERS) return ret; gcwq->flags &= ~GCWQ_MANAGE_WORKERS; gcwq->flags |= GCWQ_MANAGING_WORKERS; /* * Destroy and then create so that may_start_working() is true * on return. */ ret |= maybe_destroy_workers(gcwq); ret |= maybe_create_worker(gcwq); gcwq->flags &= ~GCWQ_MANAGING_WORKERS; /* * The trustee might be waiting to take over the manager * position, tell it we're done. */ if (unlikely(gcwq->trustee)) wake_up_all(&gcwq->trustee_wait); return ret; } /** * 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); struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq); trace_workqueue_activate_work(work); move_linked_works(work, pos, NULL); __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work)); 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 * @delayed: for a delayed work * * 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, bool delayed) { /* ignore uncolored works */ if (color == WORK_NO_COLOR) return; cwq->nr_in_flight[color]--; if (!delayed) { 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); } } /* 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) __releases(&gcwq->lock) __acquires(&gcwq->lock) { struct cpu_workqueue_struct *cwq = get_work_cwq(work); struct global_cwq *gcwq = cwq->gcwq; struct hlist_head *bwh = busy_worker_head(gcwq, work); bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE; work_func_t f = work->func; int work_color; struct worker *collision; #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 /* * A single work shouldn't be executed concurrently by * multiple workers on a single cpu. Check whether anyone is * already processing the work. If so, defer the work to the * currently executing one. */ collision = __find_worker_executing_work(gcwq, bwh, work); if (unlikely(collision)) { move_linked_works(work, &collision->scheduled, NULL); return; } /* 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); /* record the current cpu number in the work data and dequeue */ set_work_cpu(work, gcwq->cpu); list_del_init(&work->entry); /* * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI, * wake up another worker; otherwise, clear HIGHPRI_PENDING. */ if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) { struct work_struct *nwork = list_first_entry(&gcwq->worklist, struct work_struct, entry); if (!list_empty(&gcwq->worklist) && get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI) wake_up_worker(gcwq); else gcwq->flags &= ~GCWQ_HIGHPRI_PENDING; } /* * CPU intensive works don't participate in concurrency * management. They're the scheduler's responsibility. */ if (unlikely(cpu_intensive)) worker_set_flags(worker, WORKER_CPU_INTENSIVE, true); spin_unlock_irq(&gcwq->lock); work_clear_pending(work); lock_map_acquire_read(&cwq->wq->lockdep_map); lock_map_acquire(&lockdep_map); trace_workqueue_execute_start(work); f(work); /* * While we must be careful to not use "work" after this, the trace * point will only record its address. */ trace_workqueue_execute_end(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); /* clear cpu intensive status */ if (unlikely(cpu_intensive)) worker_clr_flags(worker, WORKER_CPU_INTENSIVE); /* 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, false); } /** * 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 gcwq worker thread function. There's a single dynamic pool of * these per each cpu. These workers process all works regardless of * their specific target workqueue. The only exception is works which * belong to workqueues with a rescuer which will be explained in * rescuer_thread(). */ static int worker_thread(void *__worker) { struct worker *worker = __worker; struct global_cwq *gcwq = worker->gcwq; /* tell the scheduler that this is a workqueue worker */ worker->task->flags |= PF_WQ_WORKER; 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); worker->task->flags &= ~PF_WQ_WORKER; return 0; } worker_leave_idle(worker); recheck: /* no more worker necessary? */ if (!need_more_worker(gcwq)) goto sleep; /* do we need to manage? */ if (unlikely(!may_start_working(gcwq)) && manage_workers(worker)) goto 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)); /* * When control reaches this point, we're guaranteed to have * at least one idle worker or that someone else has already * assumed the manager role. */ worker_clr_flags(worker, WORKER_PREP); do { struct work_struct *work = list_first_entry(&gcwq->worklist, struct work_struct, entry); 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); } } while (keep_working(gcwq)); worker_set_flags(worker, WORKER_PREP, false); sleep: if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker)) goto recheck; /* * gcwq->lock is held and there's no work to process and no * need to manage, sleep. Workers are woken up only while * holding gcwq->lock or from local cpu, 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; } /** * rescuer_thread - the rescuer thread function * @__wq: the associated workqueue * * Workqueue rescuer thread function. There's one rescuer for each * workqueue which has WQ_RESCUER set. * * Regular work processing on a gcwq may block trying to create a new * worker which uses GFP_KERNEL allocation which has slight chance of * developing into deadlock if some works currently on the same queue * need to be processed to satisfy the GFP_KERNEL allocation. This is * the problem rescuer solves. * * When such condition is possible, the gcwq summons rescuers of all * workqueues which have works queued on the gcwq and let them process * those works so that forward progress can be guaranteed. * * This should happen rarely. */ static int rescuer_thread(void *__wq) { struct workqueue_struct *wq = __wq; struct worker *rescuer = wq->rescuer; struct list_head *scheduled = &rescuer->scheduled; bool is_unbound = wq->flags & WQ_UNBOUND; unsigned int cpu; set_user_nice(current, RESCUER_NICE_LEVEL); repeat: set_current_state(TASK_INTERRUPTIBLE); if (kthread_should_stop()) return 0; /* * See whether any cpu is asking for help. Unbounded * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND. */ for_each_mayday_cpu(cpu, wq->mayday_mask) { unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu; struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq); struct global_cwq *gcwq = cwq->gcwq; struct work_struct *work, *n; __set_current_state(TASK_RUNNING); mayday_clear_cpu(cpu, wq->mayday_mask); /* migrate to the target cpu if possible */ rescuer->gcwq = gcwq; worker_maybe_bind_and_lock(rescuer); /* * Slurp in all works issued via this workqueue and * process'em. */ BUG_ON(!list_empty(&rescuer->scheduled)); list_for_each_entry_safe(work, n, &gcwq->worklist, entry) if (get_work_cwq(work) == cwq) move_linked_works(work, scheduled, &n); process_scheduled_works(rescuer); /* * Leave this gcwq. If keep_working() is %true, notify a * regular worker; otherwise, we end up with 0 concurrency * and stalling the execution. */ if (keep_working(gcwq)) wake_up_worker(gcwq); spin_unlock_irq(&gcwq->lock); } schedule(); goto repeat; } 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_ONSTACK(&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_cwq_cpu(cpu, wq) { 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); /* we might have raced, check again with mutex held */ if (wq->first_flusher != &this_flusher) goto out_unlock; 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); /** * drain_workqueue - drain a workqueue * @wq: workqueue to drain * * Wait until the workqueue becomes empty. While draining is in progress, * only chain queueing is allowed. IOW, only currently pending or running * work items on @wq can queue further work items on it. @wq is flushed * repeatedly until it becomes empty. The number of flushing is detemined * by the depth of chaining and should be relatively short. Whine if it * takes too long. */ void drain_workqueue(struct workqueue_struct *wq) { unsigned int flush_cnt = 0; unsigned int cpu; /* * __queue_work() needs to test whether there are drainers, is much * hotter than drain_workqueue() and already looks at @wq->flags. * Use WQ_DRAINING so that queue doesn't have to check nr_drainers. */ spin_lock(&workqueue_lock); if (!wq->nr_drainers++) wq->flags |= WQ_DRAINING; spin_unlock(&workqueue_lock); reflush: flush_workqueue(wq); for_each_cwq_cpu(cpu, wq) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); bool drained; spin_lock_irq(&cwq->gcwq->lock); drained = !cwq->nr_active && list_empty(&cwq->delayed_works); spin_unlock_irq(&cwq->gcwq->lock); if (drained) continue; if (++flush_cnt == 10 || (flush_cnt % 100 == 0 && flush_cnt <= 1000)) pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n", wq->name, flush_cnt); goto reflush; } spin_lock(&workqueue_lock); if (!--wq->nr_drainers) wq->flags &= ~WQ_DRAINING; spin_unlock(&workqueue_lock); } EXPORT_SYMBOL_GPL(drain_workqueue); static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr, bool wait_executing) { struct worker *worker = NULL; struct global_cwq *gcwq; struct cpu_workqueue_struct *cwq; might_sleep(); gcwq = get_work_gcwq(work); if (!gcwq) return false; 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 to a different gcwq under us, we * are not going to wait. */ smp_rmb(); cwq = get_work_cwq(work); if (unlikely(!cwq || gcwq != cwq->gcwq)) goto already_gone; } else if (wait_executing) { worker = find_worker_executing_work(gcwq, work); if (!worker) goto already_gone; cwq = worker->current_cwq; } else goto already_gone; insert_wq_barrier(cwq, barr, work, worker); spin_unlock_irq(&gcwq->lock); /* * If @max_active is 1 or rescuer is in use, flushing another work * item on the same workqueue may lead to deadlock. Make sure the * flusher is not running on the same workqueue by verifying write * access. */ if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER) lock_map_acquire(&cwq->wq->lockdep_map); else lock_map_acquire_read(&cwq->wq->lockdep_map); lock_map_release(&cwq->wq->lockdep_map); return true; already_gone: spin_unlock_irq(&gcwq->lock); return false; } /** * flush_work - wait for a work to finish executing the last queueing instance * @work: the work to flush * * Wait until @work has finished execution. This function considers * only the last queueing instance of @work. If @work has been * enqueued across different CPUs on a non-reentrant workqueue or on * multiple workqueues, @work might still be executing on return on * some of the CPUs from earlier queueing. * * If @work was queued only on a non-reentrant, ordered or unbound * workqueue, @work is guaranteed to be idle on return if it hasn't * been requeued since flush started. * * RETURNS: * %true if flush_work() waited for the work to finish execution, * %false if it was already idle. */ bool flush_work(struct work_struct *work) { struct wq_barrier barr; if (start_flush_work(work, &barr, true)) { wait_for_completion(&barr.done); destroy_work_on_stack(&barr.work); return true; } else return false; } EXPORT_SYMBOL_GPL(flush_work); static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work) { struct wq_barrier barr; struct worker *worker; spin_lock_irq(&gcwq->lock); worker = find_worker_executing_work(gcwq, work); if (unlikely(worker)) insert_wq_barrier(worker->current_cwq, &barr, work, worker); spin_unlock_irq(&gcwq->lock); if (unlikely(worker)) { wait_for_completion(&barr.done); destroy_work_on_stack(&barr.work); return true; } else return false; } static bool wait_on_work(struct work_struct *work) { bool ret = false; int cpu; might_sleep(); lock_map_acquire(&work->lockdep_map); lock_map_release(&work->lockdep_map); for_each_gcwq_cpu(cpu) ret |= wait_on_cpu_work(get_gcwq(cpu), work); return ret; } /** * flush_work_sync - wait until a work has finished execution * @work: the work to flush * * Wait until @work has finished execution. On return, it's * guaranteed that all queueing instances of @work which happened * before this function is called are finished. In other words, if * @work hasn't been requeued since this function was called, @work is * guaranteed to be idle on return. * * RETURNS: * %true if flush_work_sync() waited for the work to finish execution, * %false if it was already idle. */ bool flush_work_sync(struct work_struct *work) { struct wq_barrier barr; bool pending, waited; /* we'll wait for executions separately, queue barr only if pending */ pending = start_flush_work(work, &barr, false); /* wait for executions to finish */ waited = wait_on_work(work); /* wait for the pending one */ if (pending) { wait_for_completion(&barr.done); destroy_work_on_stack(&barr.work); } return pending || waited; } EXPORT_SYMBOL_GPL(flush_work_sync); /* * 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; 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. */ gcwq = get_work_gcwq(work); if (!gcwq) return ret; spin_lock_irq(&gcwq->lock); if (!list_empty(&work->entry)) { /* * This work is queued, but perhaps we locked the wrong gcwq. * In that case we must see the new value after rmb(), see * insert_work()->wmb(). */ smp_rmb(); if (gcwq == get_work_gcwq(work)) { debug_work_deactivate(work); list_del_init(&work->entry); cwq_dec_nr_in_flight(get_work_cwq(work), get_work_color(work), *work_data_bits(work) & WORK_STRUCT_DELAYED); ret = 1; } } spin_unlock_irq(&gcwq->lock); return ret; } static bool __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_work_data(work); return ret; } /** * cancel_work_sync - cancel a work and wait for it to finish * @work: the work to cancel * * Cancel @work and wait for its execution to finish. This function * can be used even if the work re-queues itself or migrates to * another workqueue. On return from this function, @work is * guaranteed to be not pending or executing on any CPU. * * cancel_work_sync(&delayed_work->work) must not be used for * delayed_work's. Use cancel_delayed_work_sync() instead. * * The caller must ensure that the workqueue on which @work was last * queued can't be destroyed before this function returns. * * RETURNS: * %true if @work was pending, %false otherwise. */ bool cancel_work_sync(struct work_struct *work) { return __cancel_work_timer(work, NULL); } EXPORT_SYMBOL_GPL(cancel_work_sync); /** * flush_delayed_work - wait for a dwork to finish executing the last queueing * @dwork: the delayed work to flush * * Delayed timer is cancelled and the pending work is queued for * immediate execution. Like flush_work(), this function only * considers the last queueing instance of @dwork. * * RETURNS: * %true if flush_work() waited for the work to finish execution, * %false if it was already idle. */ bool flush_delayed_work(struct delayed_work *dwork) { if (del_timer_sync(&dwork->timer)) __queue_work(raw_smp_processor_id(), get_work_cwq(&dwork->work)->wq, &dwork->work); return flush_work(&dwork->work); } EXPORT_SYMBOL(flush_delayed_work); /** * flush_delayed_work_sync - wait for a dwork to finish * @dwork: the delayed work to flush * * Delayed timer is cancelled and the pending work is queued for * execution immediately. Other than timer handling, its behavior * is identical to flush_work_sync(). * * RETURNS: * %true if flush_work_sync() waited for the work to finish execution, * %false if it was already idle. */ bool flush_delayed_work_sync(struct delayed_work *dwork) { if (del_timer_sync(&dwork->timer)) __queue_work(raw_smp_processor_id(), get_work_cwq(&dwork->work)->wq, &dwork->work); return flush_work_sync(&dwork->work); } EXPORT_SYMBOL(flush_delayed_work_sync); /** * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish * @dwork: the delayed work cancel * * This is cancel_work_sync() for delayed works. * * RETURNS: * %true if @dwork was pending, %false otherwise. */ bool cancel_delayed_work_sync(struct delayed_work *dwork) { return __cancel_work_timer(&dwork->work, &dwork->timer); } EXPORT_SYMBOL(cancel_delayed_work_sync); /** * 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(system_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, system_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(system_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, system_wq, dwork, delay); } EXPORT_SYMBOL(schedule_delayed_work_on); /** * schedule_on_each_cpu - execute a function synchronously on each online CPU * @func: the function to call * * schedule_on_each_cpu() executes @func on each online CPU using the * system workqueue and blocks until all CPUs have completed. * schedule_on_each_cpu() is very slow. * * RETURNS: * 0 on success, -errno on failure. */ int schedule_on_each_cpu(work_func_t func) { int cpu; struct work_struct __percpu *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; } /** * 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(system_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 system_wq != NULL; } static int alloc_cwqs(struct workqueue_struct *wq) { /* * 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)); #ifdef CONFIG_SMP bool percpu = !(wq->flags & WQ_UNBOUND); #else bool percpu = false; #endif if (percpu) wq->cpu_wq.pcpu = __alloc_percpu(size, align); else { void *ptr; /* * 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. */ ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL); if (ptr) { wq->cpu_wq.single = PTR_ALIGN(ptr, align); *(void **)(wq->cpu_wq.single + 1) = ptr; } } /* just in case, make sure it's actually aligned */ BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align)); return wq->cpu_wq.v ? 0 : -ENOMEM; } static void free_cwqs(struct workqueue_struct *wq) { #ifdef CONFIG_SMP bool percpu = !(wq->flags & WQ_UNBOUND); #else bool percpu = false; #endif if (percpu) free_percpu(wq->cpu_wq.pcpu); else if (wq->cpu_wq.single) { /* the pointer to free is stored right after the cwq */ kfree(*(void **)(wq->cpu_wq.single + 1)); } } static int wq_clamp_max_active(int max_active, unsigned int flags, const char *name) { int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE; if (max_active < 1 || max_active > lim) printk(KERN_WARNING "workqueue: max_active %d requested for %s " "is out of range, clamping between %d and %d\n", max_active, name, 1, lim); return clamp_val(max_active, 1, lim); } struct workqueue_struct *__alloc_workqueue_key(const char *name, unsigned int flags, int max_active, struct lock_class_key *key, const char *lock_name) { struct workqueue_struct *wq; unsigned int cpu; /* * Workqueues which may be used during memory reclaim should * have a rescuer to guarantee forward progress. */ if (flags & WQ_MEM_RECLAIM) flags |= WQ_RESCUER; /* * Unbound workqueues aren't concurrency managed and should be * dispatched to workers immediately. */ if (flags & WQ_UNBOUND) flags |= WQ_HIGHPRI; max_active = max_active ?: WQ_DFL_ACTIVE; max_active = wq_clamp_max_active(max_active, flags, name); wq = kzalloc(sizeof(*wq), GFP_KERNEL); if (!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->name = name; lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); INIT_LIST_HEAD(&wq->list); if (alloc_cwqs(wq) < 0) goto err; for_each_cwq_cpu(cpu, wq) { 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->delayed_works); } if (flags & WQ_RESCUER) { struct worker *rescuer; if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL)) goto err; wq->rescuer = rescuer = alloc_worker(); if (!rescuer) goto err; rescuer->task = kthread_create(rescuer_thread, wq, "%s", name); if (IS_ERR(rescuer->task)) goto err; rescuer->task->flags |= PF_THREAD_BOUND; wake_up_process(rescuer->task); } /* * 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_FREEZABLE) for_each_cwq_cpu(cpu, wq) get_cwq(cpu, wq)->max_active = 0; list_add(&wq->list, &workqueues); spin_unlock(&workqueue_lock); return wq; err: if (wq) { free_cwqs(wq); free_mayday_mask(wq->mayday_mask); kfree(wq->rescuer); kfree(wq); } return NULL; } EXPORT_SYMBOL_GPL(__alloc_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; /* drain it before proceeding with destruction */ drain_workqueue(wq); /* * wq list is used to freeze wq, remove from list after * flushing is complete in case freeze races us. */ spin_lock(&workqueue_lock); list_del(&wq->list); spin_unlock(&workqueue_lock); /* sanity check */ for_each_cwq_cpu(cpu, wq) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); int i; 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)); } if (wq->flags & WQ_RESCUER) { kthread_stop(wq->rescuer->task); free_mayday_mask(wq->mayday_mask); kfree(wq->rescuer); } free_cwqs(wq); kfree(wq); } EXPORT_SYMBOL_GPL(destroy_workqueue); /** * workqueue_set_max_active - adjust max_active of a workqueue * @wq: target workqueue * @max_active: new max_active value. * * Set max_active of @wq to @max_active. * * CONTEXT: * Don't call from IRQ context. */ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) { unsigned int cpu; max_active = wq_clamp_max_active(max_active, wq->flags, wq->name); spin_lock(&workqueue_lock); wq->saved_max_active = max_active; for_each_cwq_cpu(cpu, wq) { struct global_cwq *gcwq = get_gcwq(cpu); spin_lock_irq(&gcwq->lock); if (!(wq->flags & WQ_FREEZABLE) || !(gcwq->flags & GCWQ_FREEZING)) get_cwq(gcwq->cpu, wq)->max_active = max_active; spin_unlock_irq(&gcwq->lock); } spin_unlock(&workqueue_lock); } EXPORT_SYMBOL_GPL(workqueue_set_max_active); /** * workqueue_congested - test whether a workqueue is congested * @cpu: CPU in question * @wq: target workqueue * * Test whether @wq's cpu workqueue for @cpu is congested. There is * no synchronization around this function and the test result is * unreliable and only useful as advisory hints or for debugging. * * RETURNS: * %true if congested, %false otherwise. */ bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq) { struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); return !list_empty(&cwq->delayed_works); } EXPORT_SYMBOL_GPL(workqueue_congested); /** * work_cpu - return the last known associated cpu for @work * @work: the work of interest * * RETURNS: * CPU number if @work was ever queued. WORK_CPU_NONE otherwise. */ unsigned int work_cpu(struct work_struct *work) { struct global_cwq *gcwq = get_work_gcwq(work); return gcwq ? gcwq->cpu : WORK_CPU_NONE; } EXPORT_SYMBOL_GPL(work_cpu); /** * work_busy - test whether a work is currently pending or running * @work: the work to be tested * * Test whether @work is currently pending or running. There is no * synchronization around this function and the test result is * unreliable and only useful as advisory hints or for debugging. * Especially for reentrant wqs, the pending state might hide the * running state. * * RETURNS: * OR'd bitmask of WORK_BUSY_* bits. */ unsigned int work_busy(struct work_struct *work) { struct global_cwq *gcwq = get_work_gcwq(work); unsigned long flags; unsigned int ret = 0; if (!gcwq) return false; spin_lock_irqsave(&gcwq->lock, flags); if (work_pending(work)) ret |= WORK_BUSY_PENDING; if (find_worker_executing_work(gcwq, work)) ret |= WORK_BUSY_RUNNING; spin_unlock_irqrestore(&gcwq->lock, flags); return ret; } EXPORT_SYMBOL_GPL(work_busy); /* * CPU hotplug. * * There are two challenges in supporting CPU hotplug. Firstly, there * are a lot of assumptions on strong associations among work, cwq and * gcwq which make migrating pending and scheduled works very * difficult to implement without impacting hot paths. Secondly, * gcwqs serve mix of short, long and very long running works making * blocked draining impractical. * * This is solved by allowing a gcwq to be detached from CPU, running * it with unbound (rogue) workers and allowing it to be reattached * later if the cpu comes back online. A separate thread is created * to govern a gcwq in such state and is called the trustee of the * gcwq. * * 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 * assuming the manager role and 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 clears ROGUE, rebinds * all remaining workers back to the cpu and releases * manager role. * * 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 work_struct *work; struct hlist_node *pos; long rc; int i; BUG_ON(gcwq->cpu != smp_processor_id()); spin_lock_irq(&gcwq->lock); /* * Claim the manager position and make all workers rogue. * Trustee must be bound to the target cpu and can't be * cancelled. */ BUG_ON(gcwq->cpu != smp_processor_id()); rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS)); BUG_ON(rc < 0); gcwq->flags |= GCWQ_MANAGING_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; /* * Call schedule() so that we cross rq->lock and thus can * guarantee sched callbacks see the rogue flag. This is * necessary as scheduler callbacks may be invoked from other * cpus. */ spin_unlock_irq(&gcwq->lock); schedule(); spin_lock_irq(&gcwq->lock); /* * Sched callbacks are disabled now. Zap nr_running. After * this, nr_running stays zero and need_more_worker() and * keep_working() are always true as long as the worklist is * not empty. */ atomic_set(get_gcwq_nr_running(gcwq->cpu), 0); spin_unlock_irq(&gcwq->lock); del_timer_sync(&gcwq->idle_timer); spin_lock_irq(&gcwq->lock); /* * 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. We * want to get it over with ASAP - spam rescuers, wake up as * many idlers as necessary and create new ones till the * worklist is empty. Note that if the gcwq is frozen, there * may be frozen works in freezable cwqs. Don't declare * completion while frozen. */ while (gcwq->nr_workers != gcwq->nr_idle || gcwq->flags & GCWQ_FREEZING || gcwq->trustee_state == TRUSTEE_IN_CHARGE) { int nr_works = 0; list_for_each_entry(work, &gcwq->worklist, entry) { send_mayday(work); nr_works++; } list_for_each_entry(worker, &gcwq->idle_list, entry) { if (!nr_works--) break; wake_up_process(worker->task); } if (need_to_create_worker(gcwq)) { spin_unlock_irq(&gcwq->lock); worker = create_worker(gcwq, false); spin_lock_irq(&gcwq->lock); if (worker) { worker->flags |= WORKER_ROGUE; start_worker(worker); } } /* give a breather */ if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0) break; } /* * Either all works have been scheduled and cpu is down, or * cpu down has already been canceled. Wait for and butcher * all workers till we're canceled. */ do { rc = trustee_wait_event(!list_empty(&gcwq->idle_list)); while (!list_empty(&gcwq->idle_list)) destroy_worker(list_first_entry(&gcwq->idle_list, struct worker, entry)); } while (gcwq->nr_workers && rc >= 0); /* * At this point, either draining has completed and no worker * is left, or cpu down has been canceled or the cpu is being * brought back up. There shouldn't be any idle one left. * Tell the remaining busy ones to rebind once it finishes the * currently scheduled works by scheduling the rebind_work. */ WARN_ON(!list_empty(&gcwq->idle_list)); for_each_busy_worker(worker, i, pos, gcwq) { struct work_struct *rebind_work = &worker->rebind_work; /* * Rebind_work may race with future cpu hotplug * operations. Use a separate flag to mark that * rebinding is scheduled. */ worker->flags |= WORKER_REBIND; worker->flags &= ~WORKER_ROGUE; /* queue rebind_work, wq doesn't matter, use the default one */ if (test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(rebind_work))) continue; debug_work_activate(rebind_work); insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work, worker->scheduled.next, work_color_to_flags(WORK_NO_COLOR)); } /* relinquish manager role */ gcwq->flags &= ~GCWQ_MANAGING_WORKERS; /* 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) __releases(&gcwq->lock) __acquires(&gcwq->lock) { 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 *uninitialized_var(new_worker); unsigned long flags; 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); /* fall through */ case CPU_UP_PREPARE: BUG_ON(gcwq->first_idle); new_worker = create_worker(gcwq, false); if (!new_worker) { if (new_trustee) kthread_stop(new_trustee); return NOTIFY_BAD; } } /* 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); /* fall through */ case CPU_UP_PREPARE: BUG_ON(gcwq->first_idle); gcwq->first_idle = new_worker; break; case CPU_DYING: /* * Before this, the trustee and all workers except for * the ones which are still executing works from * before the last CPU down must be on the cpu. After * this, they'll all be diasporas. */ gcwq->flags |= GCWQ_DISASSOCIATED; break; case CPU_POST_DEAD: gcwq->trustee_state = TRUSTEE_BUTCHER; /* fall through */ case CPU_UP_CANCELED: destroy_worker(gcwq->first_idle); gcwq->first_idle = NULL; break; case CPU_DOWN_FAILED: case CPU_ONLINE: gcwq->flags &= ~GCWQ_DISASSOCIATED; if (gcwq->trustee_state != TRUSTEE_DONE) { gcwq->trustee_state = TRUSTEE_RELEASE; wake_up_process(gcwq->trustee); wait_trustee_state(gcwq, TRUSTEE_DONE); } /* * Trustee is done and there might be no worker left. * Put the first_idle in and request a real manager to * take a look. */ spin_unlock_irq(&gcwq->lock); kthread_bind(gcwq->first_idle->task, cpu); spin_lock_irq(&gcwq->lock); gcwq->flags |= GCWQ_MANAGE_WORKERS; start_worker(gcwq->first_idle); gcwq->first_idle = NULL; 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 freezable * workqueues will queue new works to their frozen_works list instead of * gcwq->worklist. * * CONTEXT: * Grabs and releases workqueue_lock and gcwq->lock's. */ void freeze_workqueues_begin(void) { unsigned int cpu; spin_lock(&workqueue_lock); BUG_ON(workqueue_freezing); workqueue_freezing = true; for_each_gcwq_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); struct workqueue_struct *wq; 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 (cwq && wq->flags & WQ_FREEZABLE) cwq->max_active = 0; } spin_unlock_irq(&gcwq->lock); } spin_unlock(&workqueue_lock); } /** * freeze_workqueues_busy - are freezable 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 freezable workqueues are still busy. %false if freezing * is complete. */ bool freeze_workqueues_busy(void) { unsigned int cpu; bool busy = false; spin_lock(&workqueue_lock); BUG_ON(!workqueue_freezing); for_each_gcwq_cpu(cpu) { struct workqueue_struct *wq; /* * 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 (!cwq || !(wq->flags & WQ_FREEZABLE)) 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 gcwq worklists. * * CONTEXT: * Grabs and releases workqueue_lock and gcwq->lock's. */ void thaw_workqueues(void) { unsigned int cpu; spin_lock(&workqueue_lock); if (!workqueue_freezing) goto out_unlock; for_each_gcwq_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); struct workqueue_struct *wq; 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 (!cwq || !(wq->flags & WQ_FREEZABLE)) 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); } wake_up_worker(gcwq); spin_unlock_irq(&gcwq->lock); } workqueue_freezing = false; out_unlock: spin_unlock(&workqueue_lock); } #endif /* CONFIG_FREEZER */ static int __init init_workqueues(void) { unsigned int cpu; int i; cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE); /* initialize gcwqs */ for_each_gcwq_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); spin_lock_init(&gcwq->lock); INIT_LIST_HEAD(&gcwq->worklist); gcwq->cpu = cpu; gcwq->flags |= GCWQ_DISASSOCIATED; INIT_LIST_HEAD(&gcwq->idle_list); for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) INIT_HLIST_HEAD(&gcwq->busy_hash[i]); init_timer_deferrable(&gcwq->idle_timer); gcwq->idle_timer.function = idle_worker_timeout; gcwq->idle_timer.data = (unsigned long)gcwq; setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout, (unsigned long)gcwq); ida_init(&gcwq->worker_ida); gcwq->trustee_state = TRUSTEE_DONE; init_waitqueue_head(&gcwq->trustee_wait); } /* create the initial worker */ for_each_online_gcwq_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); struct worker *worker; if (cpu != WORK_CPU_UNBOUND) gcwq->flags &= ~GCWQ_DISASSOCIATED; worker = create_worker(gcwq, true); BUG_ON(!worker); spin_lock_irq(&gcwq->lock); start_worker(worker); spin_unlock_irq(&gcwq->lock); } system_wq = alloc_workqueue("events", 0, 0); system_long_wq = alloc_workqueue("events_long", 0, 0); system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0); system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_UNBOUND_MAX_ACTIVE); system_freezable_wq = alloc_workqueue("events_freezable", WQ_FREEZABLE, 0); BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq || !system_unbound_wq || !system_freezable_wq); return 0; } early_initcall(init_workqueues);