/* * 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 #include "workqueue_internal.h" enum { /* * worker_pool flags * * A bound pool is either associated or disassociated with its CPU. * While associated (!DISASSOCIATED), all workers are bound to the * CPU and none has %WORKER_UNBOUND set and concurrency management * is in effect. * * While DISASSOCIATED, the cpu may be offline and all workers have * %WORKER_UNBOUND set and concurrency management disabled, and may * be executing on any CPU. The pool behaves as an unbound one. * * Note that DISASSOCIATED can be flipped only while holding * assoc_mutex to avoid changing binding state while * create_worker() is in progress. */ POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */ POOL_MANAGING_WORKERS = 1 << 1, /* managing workers */ POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */ POOL_FREEZING = 1 << 3, /* freeze in progress */ /* worker flags */ WORKER_STARTED = 1 << 0, /* started */ WORKER_DIE = 1 << 1, /* die die die */ WORKER_IDLE = 1 << 2, /* is idle */ WORKER_PREP = 1 << 3, /* preparing to run works */ WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */ WORKER_UNBOUND = 1 << 7, /* worker is unbound */ WORKER_NOT_RUNNING = WORKER_PREP | WORKER_UNBOUND | WORKER_CPU_INTENSIVE, NR_STD_WORKER_POOLS = 2, /* # standard pools per cpu */ BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */ 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 */ /* * Rescue workers are used only on emergencies and shared by * all cpus. Give -20. */ RESCUER_NICE_LEVEL = -20, HIGHPRI_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 POOL_DISASSOCIATED is set, it's identical to L. * * F: wq->flush_mutex protected. * * W: workqueue_lock protected. */ /* struct worker is defined in workqueue_internal.h */ struct worker_pool { struct global_cwq *gcwq; /* I: the owning gcwq */ unsigned int cpu; /* I: the associated cpu */ int id; /* I: pool ID */ unsigned int flags; /* X: flags */ struct list_head worklist; /* L: list of pending works */ int nr_workers; /* L: total number of workers */ /* nr_idle includes the ones off idle_list for rebinding */ int nr_idle; /* L: currently idle ones */ struct list_head idle_list; /* X: list of idle workers */ struct timer_list idle_timer; /* L: worker idle timeout */ struct timer_list mayday_timer; /* L: SOS timer for workers */ /* workers are chained either in busy_hash or idle_list */ DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER); /* L: hash of busy workers */ struct mutex assoc_mutex; /* protect POOL_DISASSOCIATED */ struct ida worker_ida; /* L: for worker IDs */ }; /* * 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 worker_pool pools[NR_STD_WORKER_POOLS]; /* normal and highpri pools */ } ____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 worker_pool *pool; /* I: the associated pool */ 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 */ #ifdef CONFIG_LOCKDEP struct lockdep_map lockdep_map; #endif char name[]; /* I: workqueue name */ }; struct workqueue_struct *system_wq __read_mostly; EXPORT_SYMBOL_GPL(system_wq); struct workqueue_struct *system_highpri_wq __read_mostly; EXPORT_SYMBOL_GPL(system_highpri_wq); struct workqueue_struct *system_long_wq __read_mostly; EXPORT_SYMBOL_GPL(system_long_wq); struct workqueue_struct *system_unbound_wq __read_mostly; EXPORT_SYMBOL_GPL(system_unbound_wq); struct workqueue_struct *system_freezable_wq __read_mostly; EXPORT_SYMBOL_GPL(system_freezable_wq); #define CREATE_TRACE_POINTS #include #define for_each_worker_pool(pool, gcwq) \ for ((pool) = &(gcwq)->pools[0]; \ (pool) < &(gcwq)->pools[NR_STD_WORKER_POOLS]; (pool)++) #define for_each_busy_worker(worker, i, pos, pool) \ hash_for_each(pool->busy_hash, i, pos, worker, 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, pool_nr_running[NR_STD_WORKER_POOLS]); /* * Global cpu workqueue and nr_running counter for unbound gcwq. The pools * for online CPUs have POOL_DISASSOCIATED set, and all their workers have * WORKER_UNBOUND set. */ static struct global_cwq unbound_global_cwq; static atomic_t unbound_pool_nr_running[NR_STD_WORKER_POOLS] = { [0 ... NR_STD_WORKER_POOLS - 1] = ATOMIC_INIT(0), /* always 0 */ }; /* idr of all pools */ static DEFINE_MUTEX(worker_pool_idr_mutex); static DEFINE_IDR(worker_pool_idr); static int worker_thread(void *__worker); static int std_worker_pool_pri(struct worker_pool *pool) { return pool - pool->gcwq->pools; } 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; } /* allocate ID and assign it to @pool */ static int worker_pool_assign_id(struct worker_pool *pool) { int ret; mutex_lock(&worker_pool_idr_mutex); idr_pre_get(&worker_pool_idr, GFP_KERNEL); ret = idr_get_new(&worker_pool_idr, pool, &pool->id); mutex_unlock(&worker_pool_idr_mutex); return ret; } /* * Lookup worker_pool by id. The idr currently is built during boot and * never modified. Don't worry about locking for now. */ static struct worker_pool *worker_pool_by_id(int pool_id) { return idr_find(&worker_pool_idr, pool_id); } static atomic_t *get_pool_nr_running(struct worker_pool *pool) { int cpu = pool->cpu; int idx = std_worker_pool_pri(pool); if (cpu != WORK_CPU_UNBOUND) return &per_cpu(pool_nr_running, cpu)[idx]; else return &unbound_pool_nr_running[idx]; } 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)) return per_cpu_ptr(wq->cpu_wq.pcpu, cpu); } 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; } /* * While queued, %WORK_STRUCT_CWQ is set and non flag bits of a work's data * contain the pointer to the queued cwq. Once execution starts, the flag * is cleared and the high bits contain OFFQ flags and pool ID. * * set_work_cwq(), set_work_pool_and_clear_pending(), mark_work_canceling() * and clear_work_data() can be used to set the cwq, pool or clear * work->data. These functions should only be called while the work is * owned - ie. while the PENDING bit is set. * * get_work_pool() and get_work_cwq() can be used to obtain the pool or cwq * corresponding to a work. Pool is available once the work has been * queued anywhere after initialization until it is sync canceled. cwq is * available only while the work item is queued. * * %WORK_OFFQ_CANCELING is used to mark a work item which is being * canceled. While being canceled, a work item may have its PENDING set * but stay off timer and worklist for arbitrarily long and nobody should * try to steal the PENDING bit. */ 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_pool_and_clear_pending(struct work_struct *work, int pool_id) { /* * The following wmb is paired with the implied mb in * test_and_set_bit(PENDING) and ensures all updates to @work made * here are visible to and precede any updates by the next PENDING * owner. */ smp_wmb(); set_work_data(work, (unsigned long)pool_id << WORK_OFFQ_POOL_SHIFT, 0); } static void clear_work_data(struct work_struct *work) { smp_wmb(); /* see set_work_pool_and_clear_pending() */ set_work_data(work, WORK_STRUCT_NO_POOL, 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; } /** * get_work_pool - return the worker_pool a given work was associated with * @work: the work item of interest * * Return the worker_pool @work was last associated with. %NULL if none. */ static struct worker_pool *get_work_pool(struct work_struct *work) { unsigned long data = atomic_long_read(&work->data); struct worker_pool *pool; int pool_id; if (data & WORK_STRUCT_CWQ) return ((struct cpu_workqueue_struct *) (data & WORK_STRUCT_WQ_DATA_MASK))->pool; pool_id = data >> WORK_OFFQ_POOL_SHIFT; if (pool_id == WORK_OFFQ_POOL_NONE) return NULL; pool = worker_pool_by_id(pool_id); WARN_ON_ONCE(!pool); return pool; } /** * get_work_pool_id - return the worker pool ID a given work is associated with * @work: the work item of interest * * Return the worker_pool ID @work was last associated with. * %WORK_OFFQ_POOL_NONE if none. */ static int get_work_pool_id(struct work_struct *work) { struct worker_pool *pool = get_work_pool(work); return pool ? pool->id : WORK_OFFQ_POOL_NONE; } static struct global_cwq *get_work_gcwq(struct work_struct *work) { struct worker_pool *pool = get_work_pool(work); return pool ? pool->gcwq : NULL; } static void mark_work_canceling(struct work_struct *work) { unsigned long pool_id = get_work_pool_id(work); pool_id <<= WORK_OFFQ_POOL_SHIFT; set_work_data(work, pool_id | WORK_OFFQ_CANCELING, WORK_STRUCT_PENDING); } static bool work_is_canceling(struct work_struct *work) { unsigned long data = atomic_long_read(&work->data); return !(data & WORK_STRUCT_CWQ) && (data & WORK_OFFQ_CANCELING); } /* * Policy functions. These define the policies on how the global worker * pools are managed. Unless noted otherwise, these functions assume that * they're being called with gcwq->lock held. */ static bool __need_more_worker(struct worker_pool *pool) { return !atomic_read(get_pool_nr_running(pool)); } /* * Need to wake up a worker? Called from anything but currently * running workers. * * Note that, because unbound workers never contribute to nr_running, this * function will always return %true for unbound gcwq as long as the * worklist isn't empty. */ static bool need_more_worker(struct worker_pool *pool) { return !list_empty(&pool->worklist) && __need_more_worker(pool); } /* Can I start working? Called from busy but !running workers. */ static bool may_start_working(struct worker_pool *pool) { return pool->nr_idle; } /* Do I need to keep working? Called from currently running workers. */ static bool keep_working(struct worker_pool *pool) { atomic_t *nr_running = get_pool_nr_running(pool); return !list_empty(&pool->worklist) && atomic_read(nr_running) <= 1; } /* Do we need a new worker? Called from manager. */ static bool need_to_create_worker(struct worker_pool *pool) { return need_more_worker(pool) && !may_start_working(pool); } /* Do I need to be the manager? */ static bool need_to_manage_workers(struct worker_pool *pool) { return need_to_create_worker(pool) || (pool->flags & POOL_MANAGE_WORKERS); } /* Do we have too many workers and should some go away? */ static bool too_many_workers(struct worker_pool *pool) { bool managing = pool->flags & POOL_MANAGING_WORKERS; int nr_idle = pool->nr_idle + managing; /* manager is considered idle */ int nr_busy = pool->nr_workers - nr_idle; /* * nr_idle and idle_list may disagree if idle rebinding is in * progress. Never return %true if idle_list is empty. */ if (list_empty(&pool->idle_list)) return false; 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 worker_pool *pool) { if (unlikely(list_empty(&pool->idle_list))) return NULL; return list_first_entry(&pool->idle_list, struct worker, entry); } /** * wake_up_worker - wake up an idle worker * @pool: worker pool to wake worker from * * Wake up the first idle worker of @pool. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void wake_up_worker(struct worker_pool *pool) { struct worker *worker = first_worker(pool); 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)) { WARN_ON_ONCE(worker->pool->cpu != cpu); atomic_inc(get_pool_nr_running(worker->pool)); } } /** * 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 worker_pool *pool; atomic_t *nr_running; /* * Rescuers, which may not have all the fields set up like normal * workers, also reach here, let's not access anything before * checking NOT_RUNNING. */ if (worker->flags & WORKER_NOT_RUNNING) return NULL; pool = worker->pool; nr_running = get_pool_nr_running(pool); /* 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 we're bound to and * 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(&pool->worklist)) to_wakeup = first_worker(pool); 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 worker_pool *pool = worker->pool; 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_pool_nr_running(pool); if (wakeup) { if (atomic_dec_and_test(nr_running) && !list_empty(&pool->worklist)) wake_up_worker(pool); } 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 worker_pool *pool = worker->pool; 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_pool_nr_running(pool)); } /** * find_worker_executing_work - find worker which is executing a work * @pool: pool of interest * @work: work to find worker for * * Find a worker which is executing @work on @pool by searching * @pool->busy_hash which is keyed by the address of @work. For a worker * to match, its current execution should match the address of @work and * its work function. This is to avoid unwanted dependency between * unrelated work executions through a work item being recycled while still * being executed. * * This is a bit tricky. A work item may be freed once its execution * starts and nothing prevents the freed area from being recycled for * another work item. If the same work item address ends up being reused * before the original execution finishes, workqueue will identify the * recycled work item as currently executing and make it wait until the * current execution finishes, introducing an unwanted dependency. * * This function checks the work item address, work function and workqueue * to avoid false positives. Note that this isn't complete as one may * construct a work function which can introduce dependency onto itself * through a recycled work item. Well, if somebody wants to shoot oneself * in the foot that badly, there's only so much we can do, and if such * deadlock actually occurs, it should be easy to locate the culprit work * function. * * 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 worker_pool *pool, struct work_struct *work) { struct worker *worker; struct hlist_node *tmp; hash_for_each_possible(pool->busy_hash, worker, tmp, hentry, (unsigned long)work) if (worker->current_work == work && worker->current_func == work->func) return worker; return NULL; } /** * 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_delayed_work(struct work_struct *work) { struct cpu_workqueue_struct *cwq = get_work_cwq(work); trace_workqueue_activate_work(work); move_linked_works(work, &cwq->pool->worklist, NULL); __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work)); cwq->nr_active++; } 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); cwq_activate_delayed_work(work); } /** * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight * @cwq: cwq of interest * @color: color of work which left the queue * * A work either has completed or is removed from pending queue, * decrement nr_in_flight of its cwq and handle workqueue flushing. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color) { /* ignore uncolored works */ if (color == WORK_NO_COLOR) return; cwq->nr_in_flight[color]--; cwq->nr_active--; if (!list_empty(&cwq->delayed_works)) { /* one down, submit a delayed one */ if (cwq->nr_active < cwq->max_active) cwq_activate_first_delayed(cwq); } /* 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); } /** * try_to_grab_pending - steal work item from worklist and disable irq * @work: work item to steal * @is_dwork: @work is a delayed_work * @flags: place to store irq state * * Try to grab PENDING bit of @work. This function can handle @work in any * stable state - idle, on timer or on worklist. Return values are * * 1 if @work was pending and we successfully stole PENDING * 0 if @work was idle and we claimed PENDING * -EAGAIN if PENDING couldn't be grabbed at the moment, safe to busy-retry * -ENOENT if someone else is canceling @work, this state may persist * for arbitrarily long * * On >= 0 return, the caller owns @work's PENDING bit. To avoid getting * interrupted while holding PENDING and @work off queue, irq must be * disabled on entry. This, combined with delayed_work->timer being * irqsafe, ensures that we return -EAGAIN for finite short period of time. * * On successful return, >= 0, irq is disabled and the caller is * responsible for releasing it using local_irq_restore(*@flags). * * This function is safe to call from any context including IRQ handler. */ static int try_to_grab_pending(struct work_struct *work, bool is_dwork, unsigned long *flags) { struct global_cwq *gcwq; local_irq_save(*flags); /* try to steal the timer if it exists */ if (is_dwork) { struct delayed_work *dwork = to_delayed_work(work); /* * dwork->timer is irqsafe. If del_timer() fails, it's * guaranteed that the timer is not queued anywhere and not * running on the local CPU. */ if (likely(del_timer(&dwork->timer))) return 1; } /* try to claim PENDING the normal way */ 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) goto fail; spin_lock(&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); /* * A delayed work item cannot be grabbed directly * because it might have linked NO_COLOR work items * which, if left on the delayed_list, will confuse * cwq->nr_active management later on and cause * stall. Make sure the work item is activated * before grabbing. */ if (*work_data_bits(work) & WORK_STRUCT_DELAYED) cwq_activate_delayed_work(work); list_del_init(&work->entry); cwq_dec_nr_in_flight(get_work_cwq(work), get_work_color(work)); spin_unlock(&gcwq->lock); return 1; } } spin_unlock(&gcwq->lock); fail: local_irq_restore(*flags); if (work_is_canceling(work)) return -ENOENT; cpu_relax(); return -EAGAIN; } /** * 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 worker_pool *pool = cwq->pool; /* 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(pool)) wake_up_worker(pool); } /* * 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 cpu_workqueue_struct *cwq = get_cwq(cpu, wq); struct worker_pool *pool = cwq->pool; struct global_cwq *gcwq = pool->gcwq; struct worker *worker; struct hlist_node *pos; int i; spin_lock_irqsave(&gcwq->lock, flags); for_each_busy_worker(worker, i, pos, pool) { 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 int req_cpu = cpu; /* * While a work item is PENDING && off queue, a task trying to * steal the PENDING will busy-loop waiting for it to either get * queued or lose PENDING. Grabbing PENDING and queueing should * happen with IRQ disabled. */ WARN_ON_ONCE(!irqs_disabled()); 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 worker_pool *last_pool; if (cpu == WORK_CPU_UNBOUND) cpu = raw_smp_processor_id(); /* * It's multi cpu. If @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-reentrancy. */ gcwq = get_gcwq(cpu); last_pool = get_work_pool(work); if (last_pool && last_pool->gcwq != gcwq) { struct global_cwq *last_gcwq = last_pool->gcwq; struct worker *worker; spin_lock(&last_gcwq->lock); worker = find_worker_executing_work(last_pool, work); if (worker && worker->current_cwq->wq == wq) gcwq = last_gcwq; else { /* meh... not running there, queue here */ spin_unlock(&last_gcwq->lock); spin_lock(&gcwq->lock); } } else { spin_lock(&gcwq->lock); } } else { gcwq = get_gcwq(WORK_CPU_UNBOUND); spin_lock(&gcwq->lock); } /* gcwq determined, get cwq and queue */ cwq = get_cwq(gcwq->pools[0].cpu, wq); trace_workqueue_queue_work(req_cpu, cwq, work); if (WARN_ON(!list_empty(&work->entry))) { spin_unlock(&gcwq->lock); return; } 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 = &cwq->pool->worklist; } else { work_flags |= WORK_STRUCT_DELAYED; worklist = &cwq->delayed_works; } insert_work(cwq, work, worklist, work_flags); spin_unlock(&gcwq->lock); } /** * queue_work_on - queue work on specific cpu * @cpu: CPU number to execute work on * @wq: workqueue to use * @work: work to queue * * Returns %false if @work was already on a queue, %true otherwise. * * We queue the work to a specific CPU, the caller must ensure it * can't go away. */ bool queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work) { bool ret = false; unsigned long flags; local_irq_save(flags); if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { __queue_work(cpu, wq, work); ret = true; } local_irq_restore(flags); return ret; } EXPORT_SYMBOL_GPL(queue_work_on); /** * queue_work - queue work on a workqueue * @wq: workqueue to use * @work: work to queue * * Returns %false if @work was already on a queue, %true 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. */ bool queue_work(struct workqueue_struct *wq, struct work_struct *work) { return queue_work_on(WORK_CPU_UNBOUND, wq, work); } EXPORT_SYMBOL_GPL(queue_work); 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); /* should have been called from irqsafe timer with irq already off */ __queue_work(dwork->cpu, cwq->wq, &dwork->work); } EXPORT_SYMBOL_GPL(delayed_work_timer_fn); static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, struct delayed_work *dwork, unsigned long delay) { struct timer_list *timer = &dwork->timer; struct work_struct *work = &dwork->work; unsigned int lcpu; WARN_ON_ONCE(timer->function != delayed_work_timer_fn || timer->data != (unsigned long)dwork); WARN_ON_ONCE(timer_pending(timer)); WARN_ON_ONCE(!list_empty(&work->entry)); /* * If @delay is 0, queue @dwork->work immediately. This is for * both optimization and correctness. The earliest @timer can * expire is on the closest next tick and delayed_work users depend * on that there's no such delay when @delay is 0. */ if (!delay) { __queue_work(cpu, wq, &dwork->work); return; } timer_stats_timer_set_start_info(&dwork->timer); /* * This stores cwq for the moment, for the timer_fn. Note that the * work's pool is preserved to allow reentrance detection for * delayed works. */ if (!(wq->flags & WQ_UNBOUND)) { struct worker_pool *pool = get_work_pool(work); /* * If we cannot get the last pool from @work directly, * select the last CPU such that it avoids unnecessarily * triggering non-reentrancy check in __queue_work(). */ lcpu = cpu; if (pool) lcpu = pool->cpu; if (lcpu == WORK_CPU_UNBOUND) lcpu = raw_smp_processor_id(); } else { lcpu = WORK_CPU_UNBOUND; } set_work_cwq(work, get_cwq(lcpu, wq), 0); dwork->cpu = cpu; timer->expires = jiffies + delay; if (unlikely(cpu != WORK_CPU_UNBOUND)) add_timer_on(timer, cpu); else add_timer(timer); } /** * 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 %false if @work was already on a queue, %true otherwise. If * @delay is zero and @dwork is idle, it will be scheduled for immediate * execution. */ bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, struct delayed_work *dwork, unsigned long delay) { struct work_struct *work = &dwork->work; bool ret = false; unsigned long flags; /* read the comment in __queue_work() */ local_irq_save(flags); if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { __queue_delayed_work(cpu, wq, dwork, delay); ret = true; } local_irq_restore(flags); return ret; } EXPORT_SYMBOL_GPL(queue_delayed_work_on); /** * 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 * * Equivalent to queue_delayed_work_on() but tries to use the local CPU. */ bool queue_delayed_work(struct workqueue_struct *wq, struct delayed_work *dwork, unsigned long delay) { return queue_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay); } EXPORT_SYMBOL_GPL(queue_delayed_work); /** * mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU * @cpu: CPU number to execute work on * @wq: workqueue to use * @dwork: work to queue * @delay: number of jiffies to wait before queueing * * If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise, * modify @dwork's timer so that it expires after @delay. If @delay is * zero, @work is guaranteed to be scheduled immediately regardless of its * current state. * * Returns %false if @dwork was idle and queued, %true if @dwork was * pending and its timer was modified. * * This function is safe to call from any context including IRQ handler. * See try_to_grab_pending() for details. */ bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq, struct delayed_work *dwork, unsigned long delay) { unsigned long flags; int ret; do { ret = try_to_grab_pending(&dwork->work, true, &flags); } while (unlikely(ret == -EAGAIN)); if (likely(ret >= 0)) { __queue_delayed_work(cpu, wq, dwork, delay); local_irq_restore(flags); } /* -ENOENT from try_to_grab_pending() becomes %true */ return ret; } EXPORT_SYMBOL_GPL(mod_delayed_work_on); /** * mod_delayed_work - modify delay of or queue a delayed work * @wq: workqueue to use * @dwork: work to queue * @delay: number of jiffies to wait before queueing * * mod_delayed_work_on() on local CPU. */ bool mod_delayed_work(struct workqueue_struct *wq, struct delayed_work *dwork, unsigned long delay) { return mod_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay); } EXPORT_SYMBOL_GPL(mod_delayed_work); /** * 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 worker_pool *pool = worker->pool; 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; pool->nr_idle++; worker->last_active = jiffies; /* idle_list is LIFO */ list_add(&worker->entry, &pool->idle_list); if (too_many_workers(pool) && !timer_pending(&pool->idle_timer)) mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); /* * Sanity check nr_running. Because gcwq_unbind_fn() releases * gcwq->lock between setting %WORKER_UNBOUND and zapping * nr_running, the warning may trigger spuriously. Check iff * unbind is not in progress. */ WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && pool->nr_workers == pool->nr_idle && atomic_read(get_pool_nr_running(pool))); } /** * 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 worker_pool *pool = worker->pool; BUG_ON(!(worker->flags & WORKER_IDLE)); worker_clr_flags(worker, WORKER_IDLE); pool->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 %POOL_DISASSOCIATED which is set during * %CPU_DOWN_PREPARE 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 worker_pool *pool = worker->pool; struct global_cwq *gcwq = pool->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 POOL_DISASSOCIATED. */ if (!(pool->flags & POOL_DISASSOCIATED)) set_cpus_allowed_ptr(task, get_cpu_mask(pool->cpu)); spin_lock_irq(&gcwq->lock); if (pool->flags & POOL_DISASSOCIATED) return false; if (task_cpu(task) == pool->cpu && cpumask_equal(¤t->cpus_allowed, get_cpu_mask(pool->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(); } } /* * Rebind an idle @worker to its CPU. worker_thread() will test * list_empty(@worker->entry) before leaving idle and call this function. */ static void idle_worker_rebind(struct worker *worker) { struct global_cwq *gcwq = worker->pool->gcwq; /* CPU may go down again inbetween, clear UNBOUND only on success */ if (worker_maybe_bind_and_lock(worker)) worker_clr_flags(worker, WORKER_UNBOUND); /* rebind complete, become available again */ list_add(&worker->entry, &worker->pool->idle_list); spin_unlock_irq(&gcwq->lock); } /* * Function for @worker->rebind.work used to rebind unbound 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 busy_worker_rebind_fn(struct work_struct *work) { struct worker *worker = container_of(work, struct worker, rebind_work); struct global_cwq *gcwq = worker->pool->gcwq; if (worker_maybe_bind_and_lock(worker)) worker_clr_flags(worker, WORKER_UNBOUND); spin_unlock_irq(&gcwq->lock); } /** * rebind_workers - rebind all workers of a gcwq to the associated CPU * @gcwq: gcwq of interest * * @gcwq->cpu is coming online. Rebind all workers to the CPU. Rebinding * is different for idle and busy ones. * * Idle ones will be removed from the idle_list and woken up. They will * add themselves back after completing rebind. This ensures that the * idle_list doesn't contain any unbound workers when re-bound busy workers * try to perform local wake-ups for concurrency management. * * Busy workers can rebind after they finish their current work items. * Queueing the rebind work item at the head of the scheduled list is * enough. Note that nr_running will be properly bumped as busy workers * rebind. * * On return, all non-manager workers are scheduled for rebind - see * manage_workers() for the manager special case. Any idle worker * including the manager will not appear on @idle_list until rebind is * complete, making local wake-ups safe. */ static void rebind_workers(struct global_cwq *gcwq) { struct worker_pool *pool; struct worker *worker, *n; struct hlist_node *pos; int i; lockdep_assert_held(&gcwq->lock); for_each_worker_pool(pool, gcwq) lockdep_assert_held(&pool->assoc_mutex); /* dequeue and kick idle ones */ for_each_worker_pool(pool, gcwq) { list_for_each_entry_safe(worker, n, &pool->idle_list, entry) { /* * idle workers should be off @pool->idle_list * until rebind is complete to avoid receiving * premature local wake-ups. */ list_del_init(&worker->entry); /* * worker_thread() will see the above dequeuing * and call idle_worker_rebind(). */ wake_up_process(worker->task); } /* rebind busy workers */ for_each_busy_worker(worker, i, pos, pool) { struct work_struct *rebind_work = &worker->rebind_work; struct workqueue_struct *wq; if (test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(rebind_work))) continue; debug_work_activate(rebind_work); /* * wq doesn't really matter but let's keep * @worker->pool and @cwq->pool consistent for * sanity. */ if (std_worker_pool_pri(worker->pool)) wq = system_highpri_wq; else wq = system_wq; insert_work(get_cwq(pool->cpu, wq), rebind_work, worker->scheduled.next, work_color_to_flags(WORK_NO_COLOR)); } } } 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, busy_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 * @pool: pool the new worker will belong to * * Create a new worker which is bound to @pool. 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 worker_pool *pool) { struct global_cwq *gcwq = pool->gcwq; const char *pri = std_worker_pool_pri(pool) ? "H" : ""; struct worker *worker = NULL; int id = -1; spin_lock_irq(&gcwq->lock); while (ida_get_new(&pool->worker_ida, &id)) { spin_unlock_irq(&gcwq->lock); if (!ida_pre_get(&pool->worker_ida, GFP_KERNEL)) goto fail; spin_lock_irq(&gcwq->lock); } spin_unlock_irq(&gcwq->lock); worker = alloc_worker(); if (!worker) goto fail; worker->pool = pool; worker->id = id; if (pool->cpu != WORK_CPU_UNBOUND) worker->task = kthread_create_on_node(worker_thread, worker, cpu_to_node(pool->cpu), "kworker/%u:%d%s", pool->cpu, id, pri); else worker->task = kthread_create(worker_thread, worker, "kworker/u:%d%s", id, pri); if (IS_ERR(worker->task)) goto fail; if (std_worker_pool_pri(pool)) set_user_nice(worker->task, HIGHPRI_NICE_LEVEL); /* * Determine CPU binding of the new worker depending on * %POOL_DISASSOCIATED. The caller is responsible for ensuring the * flag remains stable across this function. See the comments * above the flag definition for details. * * As an unbound worker may later become a regular one if CPU comes * online, make sure every worker has %PF_THREAD_BOUND set. */ if (!(pool->flags & POOL_DISASSOCIATED)) { kthread_bind(worker->task, pool->cpu); } else { worker->task->flags |= PF_THREAD_BOUND; worker->flags |= WORKER_UNBOUND; } return worker; fail: if (id >= 0) { spin_lock_irq(&gcwq->lock); ida_remove(&pool->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->pool->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 worker_pool *pool = worker->pool; struct global_cwq *gcwq = pool->gcwq; int id = worker->id; /* sanity check frenzy */ BUG_ON(worker->current_work); BUG_ON(!list_empty(&worker->scheduled)); if (worker->flags & WORKER_STARTED) pool->nr_workers--; if (worker->flags & WORKER_IDLE) pool->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(&pool->worker_ida, id); } static void idle_worker_timeout(unsigned long __pool) { struct worker_pool *pool = (void *)__pool; struct global_cwq *gcwq = pool->gcwq; spin_lock_irq(&gcwq->lock); if (too_many_workers(pool)) { struct worker *worker; unsigned long expires; /* idle_list is kept in LIFO order, check the last one */ worker = list_entry(pool->idle_list.prev, struct worker, entry); expires = worker->last_active + IDLE_WORKER_TIMEOUT; if (time_before(jiffies, expires)) mod_timer(&pool->idle_timer, expires); else { /* it's been idle for too long, wake up manager */ pool->flags |= POOL_MANAGE_WORKERS; wake_up_worker(pool); } } 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->pool->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 __pool) { struct worker_pool *pool = (void *)__pool; struct global_cwq *gcwq = pool->gcwq; struct work_struct *work; spin_lock_irq(&gcwq->lock); if (need_to_create_worker(pool)) { /* * 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, &pool->worklist, entry) send_mayday(work); } spin_unlock_irq(&gcwq->lock); mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL); } /** * maybe_create_worker - create a new worker if necessary * @pool: pool to create a new worker for * * Create a new worker for @pool if necessary. @pool 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 @pool 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 worker_pool *pool) __releases(&gcwq->lock) __acquires(&gcwq->lock) { struct global_cwq *gcwq = pool->gcwq; if (!need_to_create_worker(pool)) return false; restart: spin_unlock_irq(&gcwq->lock); /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */ mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT); while (true) { struct worker *worker; worker = create_worker(pool); if (worker) { del_timer_sync(&pool->mayday_timer); spin_lock_irq(&gcwq->lock); start_worker(worker); BUG_ON(need_to_create_worker(pool)); return true; } if (!need_to_create_worker(pool)) break; __set_current_state(TASK_INTERRUPTIBLE); schedule_timeout(CREATE_COOLDOWN); if (!need_to_create_worker(pool)) break; } del_timer_sync(&pool->mayday_timer); spin_lock_irq(&gcwq->lock); if (need_to_create_worker(pool)) goto restart; return true; } /** * maybe_destroy_worker - destroy workers which have been idle for a while * @pool: pool to destroy workers for * * Destroy @pool 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 worker_pool *pool) { bool ret = false; while (too_many_workers(pool)) { struct worker *worker; unsigned long expires; worker = list_entry(pool->idle_list.prev, struct worker, entry); expires = worker->last_active + IDLE_WORKER_TIMEOUT; if (time_before(jiffies, expires)) { mod_timer(&pool->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 worker_pool *pool = worker->pool; bool ret = false; if (pool->flags & POOL_MANAGING_WORKERS) return ret; pool->flags |= POOL_MANAGING_WORKERS; /* * To simplify both worker management and CPU hotplug, hold off * management while hotplug is in progress. CPU hotplug path can't * grab %POOL_MANAGING_WORKERS to achieve this because that can * lead to idle worker depletion (all become busy thinking someone * else is managing) which in turn can result in deadlock under * extreme circumstances. Use @pool->assoc_mutex to synchronize * manager against CPU hotplug. * * assoc_mutex would always be free unless CPU hotplug is in * progress. trylock first without dropping @gcwq->lock. */ if (unlikely(!mutex_trylock(&pool->assoc_mutex))) { spin_unlock_irq(&pool->gcwq->lock); mutex_lock(&pool->assoc_mutex); /* * CPU hotplug could have happened while we were waiting * for assoc_mutex. Hotplug itself can't handle us * because manager isn't either on idle or busy list, and * @gcwq's state and ours could have deviated. * * As hotplug is now excluded via assoc_mutex, we can * simply try to bind. It will succeed or fail depending * on @gcwq's current state. Try it and adjust * %WORKER_UNBOUND accordingly. */ if (worker_maybe_bind_and_lock(worker)) worker->flags &= ~WORKER_UNBOUND; else worker->flags |= WORKER_UNBOUND; ret = true; } pool->flags &= ~POOL_MANAGE_WORKERS; /* * Destroy and then create so that may_start_working() is true * on return. */ ret |= maybe_destroy_workers(pool); ret |= maybe_create_worker(pool); pool->flags &= ~POOL_MANAGING_WORKERS; mutex_unlock(&pool->assoc_mutex); return ret; } /** * 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 worker_pool *pool = worker->pool; struct global_cwq *gcwq = pool->gcwq; bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE; 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; lockdep_copy_map(&lockdep_map, &work->lockdep_map); #endif /* * Ensure we're on the correct CPU. DISASSOCIATED test is * necessary to avoid spurious warnings from rescuers servicing the * unbound or a disassociated pool. */ WARN_ON_ONCE(!(worker->flags & WORKER_UNBOUND) && !(pool->flags & POOL_DISASSOCIATED) && raw_smp_processor_id() != pool->cpu); /* * 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(pool, work); if (unlikely(collision)) { move_linked_works(work, &collision->scheduled, NULL); return; } /* claim and dequeue */ debug_work_deactivate(work); hash_add(pool->busy_hash, &worker->hentry, (unsigned long)work); worker->current_work = work; worker->current_func = work->func; worker->current_cwq = cwq; work_color = get_work_color(work); list_del_init(&work->entry); /* * 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); /* * Unbound gcwq isn't concurrency managed and work items should be * executed ASAP. Wake up another worker if necessary. */ if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool)) wake_up_worker(pool); /* * Record the last pool and clear PENDING which should be the last * update to @work. Also, do this inside @gcwq->lock so that * PENDING and queued state changes happen together while IRQ is * disabled. */ set_work_pool_and_clear_pending(work, pool->id); spin_unlock_irq(&gcwq->lock); lock_map_acquire_read(&cwq->wq->lockdep_map); lock_map_acquire(&lockdep_map); trace_workqueue_execute_start(work); worker->current_func(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)) { pr_err("BUG: workqueue leaked lock or atomic: %s/0x%08x/%d\n" " last function: %pf\n", current->comm, preempt_count(), task_pid_nr(current), worker->current_func); 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 */ hash_del(&worker->hentry); worker->current_work = NULL; worker->current_func = NULL; worker->current_cwq = NULL; cwq_dec_nr_in_flight(cwq, work_color); } /** * process_scheduled_works - process scheduled works * @worker: self * * Process all scheduled works. Please note that the scheduled list * may change while processing a work, so this function repeatedly * fetches a work from the top and executes it. * * CONTEXT: * spin_lock_irq(gcwq->lock) which may be released and regrabbed * multiple times. */ static void process_scheduled_works(struct worker *worker) { while (!list_empty(&worker->scheduled)) { struct work_struct *work = list_first_entry(&worker->scheduled, struct work_struct, entry); process_one_work(worker, work); } } /** * worker_thread - the worker thread function * @__worker: self * * The 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 worker_pool *pool = worker->pool; struct global_cwq *gcwq = pool->gcwq; /* tell the scheduler that this is a workqueue worker */ worker->task->flags |= PF_WQ_WORKER; woke_up: spin_lock_irq(&gcwq->lock); /* we are off idle list if destruction or rebind is requested */ if (unlikely(list_empty(&worker->entry))) { spin_unlock_irq(&gcwq->lock); /* if DIE is set, destruction is requested */ if (worker->flags & WORKER_DIE) { worker->task->flags &= ~PF_WQ_WORKER; return 0; } /* otherwise, rebind */ idle_worker_rebind(worker); goto woke_up; } worker_leave_idle(worker); recheck: /* no more worker necessary? */ if (!need_more_worker(pool)) goto sleep; /* do we need to manage? */ if (unlikely(!may_start_working(pool)) && 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(&pool->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(pool)); worker_set_flags(worker, WORKER_PREP, false); sleep: if (unlikely(need_to_manage_workers(pool)) && 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 * @__rescuer: self * * 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 *__rescuer) { struct worker *rescuer = __rescuer; struct workqueue_struct *wq = rescuer->rescue_wq; struct list_head *scheduled = &rescuer->scheduled; bool is_unbound = wq->flags & WQ_UNBOUND; unsigned int cpu; set_user_nice(current, RESCUER_NICE_LEVEL); /* * Mark rescuer as worker too. As WORKER_PREP is never cleared, it * doesn't participate in concurrency management. */ rescuer->task->flags |= PF_WQ_WORKER; repeat: set_current_state(TASK_INTERRUPTIBLE); if (kthread_should_stop()) { __set_current_state(TASK_RUNNING); rescuer->task->flags &= ~PF_WQ_WORKER; 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 worker_pool *pool = cwq->pool; struct global_cwq *gcwq = pool->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->pool = pool; 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, &pool->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(pool)) wake_up_worker(pool); spin_unlock_irq(&gcwq->lock); } /* rescuers should never participate in concurrency management */ WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING)); 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->pool->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->pool->gcwq->lock); drained = !cwq->nr_active && list_empty(&cwq->delayed_works); spin_unlock_irq(&cwq->pool->gcwq->lock); if (drained) continue; if (++flush_cnt == 10 || (flush_cnt % 100 == 0 && flush_cnt <= 1000)) pr_warn("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) { struct worker *worker = NULL; struct worker_pool *pool; struct global_cwq *gcwq; struct cpu_workqueue_struct *cwq; might_sleep(); pool = get_work_pool(work); if (!pool) return false; gcwq = pool->gcwq; 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->pool->gcwq)) goto already_gone; } else { worker = find_worker_executing_work(pool, work); if (!worker) goto already_gone; cwq = worker->current_cwq; } 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. @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; lock_map_acquire(&work->lockdep_map); lock_map_release(&work->lockdep_map); if (start_flush_work(work, &barr)) { wait_for_completion(&barr.done); destroy_work_on_stack(&barr.work); return true; } else { return false; } } EXPORT_SYMBOL_GPL(flush_work); static bool __cancel_work_timer(struct work_struct *work, bool is_dwork) { unsigned long flags; int ret; do { ret = try_to_grab_pending(work, is_dwork, &flags); /* * If someone else is canceling, wait for the same event it * would be waiting for before retrying. */ if (unlikely(ret == -ENOENT)) flush_work(work); } while (unlikely(ret < 0)); /* tell other tasks trying to grab @work to back off */ mark_work_canceling(work); local_irq_restore(flags); flush_work(work); 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, false); } 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) { local_irq_disable(); if (del_timer_sync(&dwork->timer)) __queue_work(dwork->cpu, get_work_cwq(&dwork->work)->wq, &dwork->work); local_irq_enable(); return flush_work(&dwork->work); } EXPORT_SYMBOL(flush_delayed_work); /** * cancel_delayed_work - cancel a delayed work * @dwork: delayed_work to cancel * * Kill off a pending delayed_work. Returns %true if @dwork was pending * and canceled; %false if wasn't pending. Note that the work callback * function may still be running on return, unless it returns %true and the * work doesn't re-arm itself. Explicitly flush or use * cancel_delayed_work_sync() to wait on it. * * This function is safe to call from any context including IRQ handler. */ bool cancel_delayed_work(struct delayed_work *dwork) { unsigned long flags; int ret; do { ret = try_to_grab_pending(&dwork->work, true, &flags); } while (unlikely(ret == -EAGAIN)); if (unlikely(ret < 0)) return false; set_work_pool_and_clear_pending(&dwork->work, get_work_pool_id(&dwork->work)); local_irq_restore(flags); return ret; } EXPORT_SYMBOL(cancel_delayed_work); /** * 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, true); } EXPORT_SYMBOL(cancel_delayed_work_sync); /** * 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 */ bool schedule_work_on(int cpu, struct work_struct *work) { return queue_work_on(cpu, system_wq, work); } EXPORT_SYMBOL(schedule_work_on); /** * schedule_work - put work task in global workqueue * @work: job to be done * * Returns %false if @work was already on the kernel-global workqueue and * %true 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. */ bool schedule_work(struct work_struct *work) { return queue_work(system_wq, work); } EXPORT_SYMBOL(schedule_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. */ bool 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_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. */ bool schedule_delayed_work(struct delayed_work *dwork, unsigned long delay) { return queue_delayed_work(system_wq, dwork, delay); } EXPORT_SYMBOL(schedule_delayed_work); /** * 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)); if (!(wq->flags & WQ_UNBOUND)) 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) { if (!(wq->flags & WQ_UNBOUND)) 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) pr_warn("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 *fmt, unsigned int flags, int max_active, struct lock_class_key *key, const char *lock_name, ...) { va_list args, args1; struct workqueue_struct *wq; unsigned int cpu; size_t namelen; /* determine namelen, allocate wq and format name */ va_start(args, lock_name); va_copy(args1, args); namelen = vsnprintf(NULL, 0, fmt, args) + 1; wq = kzalloc(sizeof(*wq) + namelen, GFP_KERNEL); if (!wq) goto err; vsnprintf(wq->name, namelen, fmt, args1); va_end(args); va_end(args1); /* * Workqueues which may be used during memory reclaim should * have a rescuer to guarantee forward progress. */ if (flags & WQ_MEM_RECLAIM) flags |= WQ_RESCUER; max_active = max_active ?: WQ_DFL_ACTIVE; max_active = wq_clamp_max_active(max_active, flags, wq->name); /* init wq */ 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); 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); int pool_idx = (bool)(flags & WQ_HIGHPRI); BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK); cwq->pool = &gcwq->pools[pool_idx]; 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->rescue_wq = wq; rescuer->task = kthread_create(rescuer_thread, rescuer, "%s", wq->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); /** * cwq_set_max_active - adjust max_active of a cwq * @cwq: target cpu_workqueue_struct * @max_active: new max_active value. * * Set @cwq->max_active to @max_active and activate delayed works if * increased. * * CONTEXT: * spin_lock_irq(gcwq->lock). */ static void cwq_set_max_active(struct cpu_workqueue_struct *cwq, int max_active) { cwq->max_active = max_active; while (!list_empty(&cwq->delayed_works) && cwq->nr_active < cwq->max_active) cwq_activate_first_delayed(cwq); } /** * 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 cpu_workqueue_struct *cwq = get_cwq(cpu, wq); struct worker_pool *pool = cwq->pool; struct global_cwq *gcwq = pool->gcwq; spin_lock_irq(&gcwq->lock); if (!(wq->flags & WQ_FREEZABLE) || !(pool->flags & POOL_FREEZING)) cwq_set_max_active(cwq, 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_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 worker_pool *pool = get_work_pool(work); struct global_cwq *gcwq; unsigned long flags; unsigned int ret = 0; if (!pool) return 0; gcwq = pool->gcwq; spin_lock_irqsave(&gcwq->lock, flags); if (work_pending(work)) ret |= WORK_BUSY_PENDING; if (find_worker_executing_work(pool, 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 the pools to be disassociated from the CPU * running as an unbound one and allowing it to be reattached later if the * cpu comes back online. */ /* claim manager positions of all pools */ static void gcwq_claim_assoc_and_lock(struct global_cwq *gcwq) { struct worker_pool *pool; for_each_worker_pool(pool, gcwq) mutex_lock_nested(&pool->assoc_mutex, pool - gcwq->pools); spin_lock_irq(&gcwq->lock); } /* release manager positions */ static void gcwq_release_assoc_and_unlock(struct global_cwq *gcwq) { struct worker_pool *pool; spin_unlock_irq(&gcwq->lock); for_each_worker_pool(pool, gcwq) mutex_unlock(&pool->assoc_mutex); } static void gcwq_unbind_fn(struct work_struct *work) { struct global_cwq *gcwq = get_gcwq(smp_processor_id()); struct worker_pool *pool; struct worker *worker; struct hlist_node *pos; int i; BUG_ON(gcwq->pools[0].cpu != smp_processor_id()); gcwq_claim_assoc_and_lock(gcwq); /* * We've claimed all manager positions. Make all workers unbound * and set DISASSOCIATED. Before this, 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 may become diasporas. */ for_each_worker_pool(pool, gcwq) { list_for_each_entry(worker, &pool->idle_list, entry) worker->flags |= WORKER_UNBOUND; for_each_busy_worker(worker, i, pos, pool) worker->flags |= WORKER_UNBOUND; pool->flags |= POOL_DISASSOCIATED; } gcwq_release_assoc_and_unlock(gcwq); /* * Call schedule() so that we cross rq->lock and thus can guarantee * sched callbacks see the %WORKER_UNBOUND flag. This is necessary * as scheduler callbacks may be invoked from other cpus. */ schedule(); /* * 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. @gcwq now * behaves as unbound (in terms of concurrency management) gcwq * which is served by workers tied to the CPU. * * On return from this function, the current worker would trigger * unbound chain execution of pending work items if other workers * didn't already. */ for_each_worker_pool(pool, gcwq) atomic_set(get_pool_nr_running(pool), 0); } /* * Workqueues should be brought up before normal priority CPU notifiers. * This will be registered high priority CPU notifier. */ static int __cpuinit workqueue_cpu_up_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { unsigned int cpu = (unsigned long)hcpu; struct global_cwq *gcwq = get_gcwq(cpu); struct worker_pool *pool; switch (action & ~CPU_TASKS_FROZEN) { case CPU_UP_PREPARE: for_each_worker_pool(pool, gcwq) { struct worker *worker; if (pool->nr_workers) continue; worker = create_worker(pool); if (!worker) return NOTIFY_BAD; spin_lock_irq(&gcwq->lock); start_worker(worker); spin_unlock_irq(&gcwq->lock); } break; case CPU_DOWN_FAILED: case CPU_ONLINE: gcwq_claim_assoc_and_lock(gcwq); for_each_worker_pool(pool, gcwq) pool->flags &= ~POOL_DISASSOCIATED; rebind_workers(gcwq); gcwq_release_assoc_and_unlock(gcwq); break; } return NOTIFY_OK; } /* * Workqueues should be brought down after normal priority CPU notifiers. * This will be registered as low priority CPU notifier. */ static int __cpuinit workqueue_cpu_down_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { unsigned int cpu = (unsigned long)hcpu; struct work_struct unbind_work; switch (action & ~CPU_TASKS_FROZEN) { case CPU_DOWN_PREPARE: /* unbinding should happen on the local CPU */ INIT_WORK_ONSTACK(&unbind_work, gcwq_unbind_fn); queue_work_on(cpu, system_highpri_wq, &unbind_work); flush_work(&unbind_work); break; } return NOTIFY_OK; } #ifdef CONFIG_SMP struct work_for_cpu { struct work_struct work; long (*fn)(void *); void *arg; long ret; }; static void work_for_cpu_fn(struct work_struct *work) { struct work_for_cpu *wfc = container_of(work, struct work_for_cpu, work); wfc->ret = wfc->fn(wfc->arg); } /** * work_on_cpu - run a function in user context on a particular cpu * @cpu: the cpu to run on * @fn: the function to run * @arg: the function arg * * This will return 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 work_for_cpu wfc = { .fn = fn, .arg = arg }; INIT_WORK_ONSTACK(&wfc.work, work_for_cpu_fn); schedule_work_on(cpu, &wfc.work); flush_work(&wfc.work); 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 worker_pool *pool; struct workqueue_struct *wq; spin_lock_irq(&gcwq->lock); for_each_worker_pool(pool, gcwq) { WARN_ON_ONCE(pool->flags & POOL_FREEZING); pool->flags |= POOL_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 worker_pool *pool; struct workqueue_struct *wq; spin_lock_irq(&gcwq->lock); for_each_worker_pool(pool, gcwq) { WARN_ON_ONCE(!(pool->flags & POOL_FREEZING)); pool->flags &= ~POOL_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_set_max_active(cwq, wq->saved_max_active); } for_each_worker_pool(pool, gcwq) wake_up_worker(pool); 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; /* make sure we have enough bits for OFFQ pool ID */ BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT)) < WORK_CPU_LAST * NR_STD_WORKER_POOLS); cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP); hotcpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN); /* initialize gcwqs */ for_each_gcwq_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); struct worker_pool *pool; spin_lock_init(&gcwq->lock); for_each_worker_pool(pool, gcwq) { pool->gcwq = gcwq; pool->cpu = cpu; pool->flags |= POOL_DISASSOCIATED; INIT_LIST_HEAD(&pool->worklist); INIT_LIST_HEAD(&pool->idle_list); hash_init(pool->busy_hash); init_timer_deferrable(&pool->idle_timer); pool->idle_timer.function = idle_worker_timeout; pool->idle_timer.data = (unsigned long)pool; setup_timer(&pool->mayday_timer, gcwq_mayday_timeout, (unsigned long)pool); mutex_init(&pool->assoc_mutex); ida_init(&pool->worker_ida); /* alloc pool ID */ BUG_ON(worker_pool_assign_id(pool)); } } /* create the initial worker */ for_each_online_gcwq_cpu(cpu) { struct global_cwq *gcwq = get_gcwq(cpu); struct worker_pool *pool; for_each_worker_pool(pool, gcwq) { struct worker *worker; if (cpu != WORK_CPU_UNBOUND) pool->flags &= ~POOL_DISASSOCIATED; worker = create_worker(pool); BUG_ON(!worker); spin_lock_irq(&gcwq->lock); start_worker(worker); spin_unlock_irq(&gcwq->lock); } } system_wq = alloc_workqueue("events", 0, 0); system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0); system_long_wq = alloc_workqueue("events_long", 0, 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_highpri_wq || !system_long_wq || !system_unbound_wq || !system_freezable_wq); return 0; } early_initcall(init_workqueues);