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Diffstat (limited to 'kernel/workqueue.c')
-rw-r--r-- | kernel/workqueue.c | 3813 |
1 files changed, 3813 insertions, 0 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c new file mode 100644 index 00000000..ee1845b8 --- /dev/null +++ b/kernel/workqueue.c @@ -0,0 +1,3813 @@ +/* + * kernel/workqueue.c - generic async execution with shared worker pool + * + * Copyright (C) 2002 Ingo Molnar + * + * Derived from the taskqueue/keventd code by: + * David Woodhouse <dwmw2@infradead.org> + * Andrew Morton + * Kai Petzke <wpp@marie.physik.tu-berlin.de> + * Theodore Ts'o <tytso@mit.edu> + * + * Made to use alloc_percpu by Christoph Lameter. + * + * Copyright (C) 2010 SUSE Linux Products GmbH + * Copyright (C) 2010 Tejun Heo <tj@kernel.org> + * + * 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 <linux/module.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/init.h> +#include <linux/signal.h> +#include <linux/completion.h> +#include <linux/workqueue.h> +#include <linux/slab.h> +#include <linux/cpu.h> +#include <linux/notifier.h> +#include <linux/kthread.h> +#include <linux/hardirq.h> +#include <linux/mempolicy.h> +#include <linux/freezer.h> +#include <linux/kallsyms.h> +#include <linux/debug_locks.h> +#include <linux/lockdep.h> +#include <linux/idr.h> + +#include "workqueue_sched.h" + +enum { + /* global_cwq flags */ + GCWQ_MANAGE_WORKERS = 1 << 0, /* need to manage workers */ + GCWQ_MANAGING_WORKERS = 1 << 1, /* managing workers */ + GCWQ_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */ + GCWQ_FREEZING = 1 << 3, /* freeze in progress */ + GCWQ_HIGHPRI_PENDING = 1 << 4, /* highpri works on queue */ + + /* worker flags */ + WORKER_STARTED = 1 << 0, /* started */ + WORKER_DIE = 1 << 1, /* die die die */ + WORKER_IDLE = 1 << 2, /* is idle */ + WORKER_PREP = 1 << 3, /* preparing to run works */ + WORKER_ROGUE = 1 << 4, /* not bound to any cpu */ + WORKER_REBIND = 1 << 5, /* mom is home, come back */ + WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */ + WORKER_UNBOUND = 1 << 7, /* worker is unbound */ + + WORKER_NOT_RUNNING = WORKER_PREP | WORKER_ROGUE | WORKER_REBIND | + WORKER_CPU_INTENSIVE | WORKER_UNBOUND, + + /* gcwq->trustee_state */ + TRUSTEE_START = 0, /* start */ + TRUSTEE_IN_CHARGE = 1, /* trustee in charge of gcwq */ + TRUSTEE_BUTCHER = 2, /* butcher workers */ + TRUSTEE_RELEASE = 3, /* release workers */ + TRUSTEE_DONE = 4, /* trustee is done */ + + BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */ + BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER, + BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1, + + MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */ + IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */ + + MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2, + /* call for help after 10ms + (min two ticks) */ + MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */ + CREATE_COOLDOWN = HZ, /* time to breath after fail */ + TRUSTEE_COOLDOWN = HZ / 10, /* for trustee draining */ + + /* + * Rescue workers are used only on emergencies and shared by + * all cpus. Give -20. + */ + RESCUER_NICE_LEVEL = -20, +}; + +/* + * Structure fields follow one of the following exclusion rules. + * + * I: Modifiable by initialization/destruction paths and read-only for + * everyone else. + * + * P: Preemption protected. Disabling preemption is enough and should + * only be modified and accessed from the local cpu. + * + * L: gcwq->lock protected. Access with gcwq->lock held. + * + * X: During normal operation, modification requires gcwq->lock and + * should be done only from local cpu. Either disabling preemption + * on local cpu or grabbing gcwq->lock is enough for read access. + * If GCWQ_DISASSOCIATED is set, it's identical to L. + * + * F: wq->flush_mutex protected. + * + * W: workqueue_lock protected. + */ + +struct global_cwq; + +/* + * The poor guys doing the actual heavy lifting. All on-duty workers + * are either serving the manager role, on idle list or on busy hash. + */ +struct worker { + /* on idle list while idle, on busy hash table while busy */ + union { + struct list_head entry; /* L: while idle */ + struct hlist_node hentry; /* L: while busy */ + }; + + struct work_struct *current_work; /* L: work being processed */ + struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */ + struct list_head scheduled; /* L: scheduled works */ + struct task_struct *task; /* I: worker task */ + struct global_cwq *gcwq; /* I: the associated gcwq */ + /* 64 bytes boundary on 64bit, 32 on 32bit */ + unsigned long last_active; /* L: last active timestamp */ + unsigned int flags; /* X: flags */ + int id; /* I: worker id */ + struct work_struct rebind_work; /* L: rebind worker to cpu */ +}; + +/* + * Global per-cpu workqueue. There's one and only one for each cpu + * and all works are queued and processed here regardless of their + * target workqueues. + */ +struct global_cwq { + spinlock_t lock; /* the gcwq lock */ + struct list_head worklist; /* L: list of pending works */ + unsigned int cpu; /* I: the associated cpu */ + unsigned int flags; /* L: GCWQ_* flags */ + + int nr_workers; /* L: total number of workers */ + int nr_idle; /* L: currently idle ones */ + + /* workers are chained either in the idle_list or busy_hash */ + struct list_head idle_list; /* X: list of idle workers */ + struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE]; + /* L: hash of busy workers */ + + struct timer_list idle_timer; /* L: worker idle timeout */ + struct timer_list mayday_timer; /* L: SOS timer for dworkers */ + + struct ida worker_ida; /* L: for worker IDs */ + + struct task_struct *trustee; /* L: for gcwq shutdown */ + unsigned int trustee_state; /* L: trustee state */ + wait_queue_head_t trustee_wait; /* trustee wait */ + struct worker *first_idle; /* L: first idle worker */ +} ____cacheline_aligned_in_smp; + +/* + * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of + * work_struct->data are used for flags and thus cwqs need to be + * aligned at two's power of the number of flag bits. + */ +struct cpu_workqueue_struct { + struct global_cwq *gcwq; /* I: the associated gcwq */ + struct workqueue_struct *wq; /* I: the owning workqueue */ + int work_color; /* L: current color */ + int flush_color; /* L: flushing color */ + int nr_in_flight[WORK_NR_COLORS]; + /* L: nr of in_flight works */ + int nr_active; /* L: nr of active works */ + int max_active; /* L: max active works */ + struct list_head delayed_works; /* L: delayed works */ +}; + +/* + * Structure used to wait for workqueue flush. + */ +struct wq_flusher { + struct list_head list; /* F: list of flushers */ + int flush_color; /* F: flush color waiting for */ + struct completion done; /* flush completion */ +}; + +/* + * All cpumasks are assumed to be always set on UP and thus can't be + * used to determine whether there's something to be done. + */ +#ifdef CONFIG_SMP +typedef cpumask_var_t mayday_mask_t; +#define mayday_test_and_set_cpu(cpu, mask) \ + cpumask_test_and_set_cpu((cpu), (mask)) +#define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask)) +#define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask)) +#define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp)) +#define free_mayday_mask(mask) free_cpumask_var((mask)) +#else +typedef unsigned long mayday_mask_t; +#define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask)) +#define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask)) +#define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask)) +#define alloc_mayday_mask(maskp, gfp) true +#define free_mayday_mask(mask) do { } while (0) +#endif + +/* + * The externally visible workqueue abstraction is an array of + * per-CPU workqueues: + */ +struct workqueue_struct { + unsigned int flags; /* I: 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 saved_max_active; /* W: saved cwq max_active */ + const char *name; /* I: workqueue name */ +#ifdef CONFIG_LOCKDEP + struct lockdep_map lockdep_map; +#endif +}; + +struct workqueue_struct *system_wq __read_mostly; +struct workqueue_struct *system_long_wq __read_mostly; +struct workqueue_struct *system_nrt_wq __read_mostly; +struct workqueue_struct *system_unbound_wq __read_mostly; +struct workqueue_struct *system_freezable_wq __read_mostly; +struct workqueue_struct *system_nrt_freezable_wq __read_mostly; +EXPORT_SYMBOL_GPL(system_wq); +EXPORT_SYMBOL_GPL(system_long_wq); +EXPORT_SYMBOL_GPL(system_nrt_wq); +EXPORT_SYMBOL_GPL(system_unbound_wq); +EXPORT_SYMBOL_GPL(system_freezable_wq); +EXPORT_SYMBOL_GPL(system_nrt_freezable_wq); + +#define CREATE_TRACE_POINTS +#include <trace/events/workqueue.h> + +#define for_each_busy_worker(worker, i, pos, gcwq) \ + for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \ + hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry) + +static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask, + unsigned int sw) +{ + if (cpu < nr_cpu_ids) { + if (sw & 1) { + cpu = cpumask_next(cpu, mask); + if (cpu < nr_cpu_ids) + return cpu; + } + if (sw & 2) + return WORK_CPU_UNBOUND; + } + return WORK_CPU_NONE; +} + +static inline int __next_wq_cpu(int cpu, const struct cpumask *mask, + struct workqueue_struct *wq) +{ + return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2); +} + +/* + * CPU iterators + * + * An extra gcwq is defined for an invalid cpu number + * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any + * specific CPU. The following iterators are similar to + * for_each_*_cpu() iterators but also considers the unbound gcwq. + * + * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND + * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND + * for_each_cwq_cpu() : possible CPUs for bound workqueues, + * WORK_CPU_UNBOUND for unbound workqueues + */ +#define for_each_gcwq_cpu(cpu) \ + for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \ + (cpu) < WORK_CPU_NONE; \ + (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3)) + +#define for_each_online_gcwq_cpu(cpu) \ + for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \ + (cpu) < WORK_CPU_NONE; \ + (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3)) + +#define for_each_cwq_cpu(cpu, wq) \ + for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \ + (cpu) < WORK_CPU_NONE; \ + (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq))) + +#ifdef CONFIG_DEBUG_OBJECTS_WORK + +static struct debug_obj_descr work_debug_descr; + +static void *work_debug_hint(void *addr) +{ + return ((struct work_struct *) addr)->func; +} + +/* + * fixup_init is called when: + * - an active object is initialized + */ +static int work_fixup_init(void *addr, enum debug_obj_state state) +{ + struct work_struct *work = addr; + + switch (state) { + case ODEBUG_STATE_ACTIVE: + cancel_work_sync(work); + debug_object_init(work, &work_debug_descr); + return 1; + default: + return 0; + } +} + +/* + * fixup_activate is called when: + * - an active object is activated + * - an unknown object is activated (might be a statically initialized object) + */ +static int work_fixup_activate(void *addr, enum debug_obj_state state) +{ + struct work_struct *work = addr; + + switch (state) { + + case ODEBUG_STATE_NOTAVAILABLE: + /* + * This is not really a fixup. The work struct was + * statically initialized. We just make sure that it + * is tracked in the object tracker. + */ + if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) { + debug_object_init(work, &work_debug_descr); + debug_object_activate(work, &work_debug_descr); + return 0; + } + WARN_ON_ONCE(1); + return 0; + + case ODEBUG_STATE_ACTIVE: + WARN_ON(1); + + default: + return 0; + } +} + +/* + * fixup_free is called when: + * - an active object is freed + */ +static int work_fixup_free(void *addr, enum debug_obj_state state) +{ + struct work_struct *work = addr; + + switch (state) { + case ODEBUG_STATE_ACTIVE: + cancel_work_sync(work); + debug_object_free(work, &work_debug_descr); + return 1; + default: + return 0; + } +} + +static struct debug_obj_descr work_debug_descr = { + .name = "work_struct", + .debug_hint = work_debug_hint, + .fixup_init = work_fixup_init, + .fixup_activate = work_fixup_activate, + .fixup_free = work_fixup_free, +}; + +static inline void debug_work_activate(struct work_struct *work) +{ + debug_object_activate(work, &work_debug_descr); +} + +static inline void debug_work_deactivate(struct work_struct *work) +{ + debug_object_deactivate(work, &work_debug_descr); +} + +void __init_work(struct work_struct *work, int onstack) +{ + if (onstack) + debug_object_init_on_stack(work, &work_debug_descr); + else + debug_object_init(work, &work_debug_descr); +} +EXPORT_SYMBOL_GPL(__init_work); + +void destroy_work_on_stack(struct work_struct *work) +{ + debug_object_free(work, &work_debug_descr); +} +EXPORT_SYMBOL_GPL(destroy_work_on_stack); + +#else +static inline void debug_work_activate(struct work_struct *work) { } +static inline void debug_work_deactivate(struct work_struct *work) { } +#endif + +/* Serializes the accesses to the list of workqueues. */ +static DEFINE_SPINLOCK(workqueue_lock); +static LIST_HEAD(workqueues); +static bool workqueue_freezing; /* W: have wqs started freezing? */ + +/* + * The almighty global cpu workqueues. nr_running is the only field + * which is expected to be used frequently by other cpus via + * try_to_wake_up(). Put it in a separate cacheline. + */ +static DEFINE_PER_CPU(struct global_cwq, global_cwq); +static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, gcwq_nr_running); + +/* + * Global cpu workqueue and nr_running counter for unbound gcwq. The + * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its + * workers have WORKER_UNBOUND set. + */ +static struct global_cwq unbound_global_cwq; +static atomic_t unbound_gcwq_nr_running = ATOMIC_INIT(0); /* always 0 */ + +static int worker_thread(void *__worker); + +static struct global_cwq *get_gcwq(unsigned int cpu) +{ + if (cpu != WORK_CPU_UNBOUND) + return &per_cpu(global_cwq, cpu); + else + return &unbound_global_cwq; +} + +static atomic_t *get_gcwq_nr_running(unsigned int cpu) +{ + if (cpu != WORK_CPU_UNBOUND) + return &per_cpu(gcwq_nr_running, cpu); + else + return &unbound_gcwq_nr_running; +} + +static struct cpu_workqueue_struct *get_cwq(unsigned int cpu, + struct workqueue_struct *wq) +{ + if (!(wq->flags & WQ_UNBOUND)) { + if (likely(cpu < nr_cpu_ids)) { +#ifdef CONFIG_SMP + return per_cpu_ptr(wq->cpu_wq.pcpu, cpu); +#else + return wq->cpu_wq.single; +#endif + } + } else if (likely(cpu == WORK_CPU_UNBOUND)) + return wq->cpu_wq.single; + return NULL; +} + +static unsigned int work_color_to_flags(int color) +{ + return color << WORK_STRUCT_COLOR_SHIFT; +} + +static int get_work_color(struct work_struct *work) +{ + return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) & + ((1 << WORK_STRUCT_COLOR_BITS) - 1); +} + +static int work_next_color(int color) +{ + return (color + 1) % WORK_NR_COLORS; +} + +/* + * A work's data points to the cwq with WORK_STRUCT_CWQ set while the + * work is on queue. Once execution starts, WORK_STRUCT_CWQ is + * cleared and the work data contains the cpu number it was last on. + * + * set_work_{cwq|cpu}() and clear_work_data() can be used to set the + * cwq, cpu or clear work->data. These functions should only be + * called while the work is owned - ie. while the PENDING bit is set. + * + * get_work_[g]cwq() can be used to obtain the gcwq or cwq + * corresponding to a work. gcwq is available once the work has been + * queued anywhere after initialization. cwq is available only from + * queueing until execution starts. + */ +static inline void set_work_data(struct work_struct *work, unsigned long data, + unsigned long flags) +{ + BUG_ON(!work_pending(work)); + atomic_long_set(&work->data, data | flags | work_static(work)); +} + +static void set_work_cwq(struct work_struct *work, + struct cpu_workqueue_struct *cwq, + unsigned long extra_flags) +{ + set_work_data(work, (unsigned long)cwq, + WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags); +} + +static void set_work_cpu(struct work_struct *work, unsigned int cpu) +{ + set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING); +} + +static void clear_work_data(struct work_struct *work) +{ + set_work_data(work, WORK_STRUCT_NO_CPU, 0); +} + +static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work) +{ + unsigned long data = atomic_long_read(&work->data); + + if (data & WORK_STRUCT_CWQ) + return (void *)(data & WORK_STRUCT_WQ_DATA_MASK); + else + return NULL; +} + +static struct global_cwq *get_work_gcwq(struct work_struct *work) +{ + unsigned long data = atomic_long_read(&work->data); + unsigned int cpu; + + if (data & WORK_STRUCT_CWQ) + return ((struct cpu_workqueue_struct *) + (data & WORK_STRUCT_WQ_DATA_MASK))->gcwq; + + cpu = data >> WORK_STRUCT_FLAG_BITS; + if (cpu == WORK_CPU_NONE) + return NULL; + + BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND); + return get_gcwq(cpu); +} + +/* + * Policy functions. These define the policies on how the global + * worker pool is managed. Unless noted otherwise, these functions + * assume that they're being called with gcwq->lock held. + */ + +static bool __need_more_worker(struct global_cwq *gcwq) +{ + return !atomic_read(get_gcwq_nr_running(gcwq->cpu)) || + gcwq->flags & GCWQ_HIGHPRI_PENDING; +} + +/* + * Need to wake up a worker? Called from anything but currently + * running workers. + */ +static bool need_more_worker(struct global_cwq *gcwq) +{ + return !list_empty(&gcwq->worklist) && __need_more_worker(gcwq); +} + +/* Can I start working? Called from busy but !running workers. */ +static bool may_start_working(struct global_cwq *gcwq) +{ + return gcwq->nr_idle; +} + +/* Do I need to keep working? Called from currently running workers. */ +static bool keep_working(struct global_cwq *gcwq) +{ + atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu); + + return !list_empty(&gcwq->worklist) && + (atomic_read(nr_running) <= 1 || + gcwq->flags & GCWQ_HIGHPRI_PENDING); +} + +/* Do we need a new worker? Called from manager. */ +static bool need_to_create_worker(struct global_cwq *gcwq) +{ + return need_more_worker(gcwq) && !may_start_working(gcwq); +} + +/* Do I need to be the manager? */ +static bool need_to_manage_workers(struct global_cwq *gcwq) +{ + return need_to_create_worker(gcwq) || gcwq->flags & GCWQ_MANAGE_WORKERS; +} + +/* Do we have too many workers and should some go away? */ +static bool too_many_workers(struct global_cwq *gcwq) +{ + bool managing = gcwq->flags & GCWQ_MANAGING_WORKERS; + int nr_idle = gcwq->nr_idle + managing; /* manager is considered idle */ + int nr_busy = gcwq->nr_workers - nr_idle; + + return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy; +} + +/* + * Wake up functions. + */ + +/* Return the first worker. Safe with preemption disabled */ +static struct worker *first_worker(struct global_cwq *gcwq) +{ + if (unlikely(list_empty(&gcwq->idle_list))) + return NULL; + + return list_first_entry(&gcwq->idle_list, struct worker, entry); +} + +/** + * wake_up_worker - wake up an idle worker + * @gcwq: gcwq to wake worker for + * + * Wake up the first idle worker of @gcwq. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + */ +static void wake_up_worker(struct global_cwq *gcwq) +{ + struct worker *worker = first_worker(gcwq); + + if (likely(worker)) + wake_up_process(worker->task); +} + +/** + * wq_worker_waking_up - a worker is waking up + * @task: task waking up + * @cpu: CPU @task is waking up to + * + * This function is called during try_to_wake_up() when a worker is + * being awoken. + * + * CONTEXT: + * spin_lock_irq(rq->lock) + */ +void wq_worker_waking_up(struct task_struct *task, unsigned int cpu) +{ + struct worker *worker = kthread_data(task); + + if (!(worker->flags & WORKER_NOT_RUNNING)) + atomic_inc(get_gcwq_nr_running(cpu)); +} + +/** + * wq_worker_sleeping - a worker is going to sleep + * @task: task going to sleep + * @cpu: CPU in question, must be the current CPU number + * + * This function is called during schedule() when a busy worker is + * going to sleep. Worker on the same cpu can be woken up by + * returning pointer to its task. + * + * CONTEXT: + * spin_lock_irq(rq->lock) + * + * RETURNS: + * Worker task on @cpu to wake up, %NULL if none. + */ +struct task_struct *wq_worker_sleeping(struct task_struct *task, + unsigned int cpu) +{ + struct worker *worker = kthread_data(task), *to_wakeup = NULL; + struct global_cwq *gcwq = get_gcwq(cpu); + atomic_t *nr_running = get_gcwq_nr_running(cpu); + + if (worker->flags & WORKER_NOT_RUNNING) + return NULL; + + /* this can only happen on the local cpu */ + BUG_ON(cpu != raw_smp_processor_id()); + + /* + * The counterpart of the following dec_and_test, implied mb, + * worklist not empty test sequence is in insert_work(). + * Please read comment there. + * + * NOT_RUNNING is clear. This means that trustee is not in + * charge and we're running on the local cpu w/ rq lock held + * and preemption disabled, which in turn means that none else + * could be manipulating idle_list, so dereferencing idle_list + * without gcwq lock is safe. + */ + if (atomic_dec_and_test(nr_running) && !list_empty(&gcwq->worklist)) + to_wakeup = first_worker(gcwq); + return to_wakeup ? to_wakeup->task : NULL; +} + +/** + * worker_set_flags - set worker flags and adjust nr_running accordingly + * @worker: self + * @flags: flags to set + * @wakeup: wakeup an idle worker if necessary + * + * Set @flags in @worker->flags and adjust nr_running accordingly. If + * nr_running becomes zero and @wakeup is %true, an idle worker is + * woken up. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) + */ +static inline void worker_set_flags(struct worker *worker, unsigned int flags, + bool wakeup) +{ + struct global_cwq *gcwq = worker->gcwq; + + WARN_ON_ONCE(worker->task != current); + + /* + * If transitioning into NOT_RUNNING, adjust nr_running and + * wake up an idle worker as necessary if requested by + * @wakeup. + */ + if ((flags & WORKER_NOT_RUNNING) && + !(worker->flags & WORKER_NOT_RUNNING)) { + atomic_t *nr_running = get_gcwq_nr_running(gcwq->cpu); + + if (wakeup) { + if (atomic_dec_and_test(nr_running) && + !list_empty(&gcwq->worklist)) + wake_up_worker(gcwq); + } else + atomic_dec(nr_running); + } + + worker->flags |= flags; +} + +/** + * worker_clr_flags - clear worker flags and adjust nr_running accordingly + * @worker: self + * @flags: flags to clear + * + * Clear @flags in @worker->flags and adjust nr_running accordingly. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) + */ +static inline void worker_clr_flags(struct worker *worker, unsigned int flags) +{ + struct global_cwq *gcwq = worker->gcwq; + unsigned int oflags = worker->flags; + + WARN_ON_ONCE(worker->task != current); + + worker->flags &= ~flags; + + /* + * If transitioning out of NOT_RUNNING, increment nr_running. Note + * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask + * of multiple flags, not a single flag. + */ + if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING)) + if (!(worker->flags & WORKER_NOT_RUNNING)) + atomic_inc(get_gcwq_nr_running(gcwq->cpu)); +} + +/** + * busy_worker_head - return the busy hash head for a work + * @gcwq: gcwq of interest + * @work: work to be hashed + * + * Return hash head of @gcwq for @work. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + * + * RETURNS: + * Pointer to the hash head. + */ +static struct hlist_head *busy_worker_head(struct global_cwq *gcwq, + struct work_struct *work) +{ + const int base_shift = ilog2(sizeof(struct work_struct)); + unsigned long v = (unsigned long)work; + + /* simple shift and fold hash, do we need something better? */ + v >>= base_shift; + v += v >> BUSY_WORKER_HASH_ORDER; + v &= BUSY_WORKER_HASH_MASK; + + return &gcwq->busy_hash[v]; +} + +/** + * __find_worker_executing_work - find worker which is executing a work + * @gcwq: gcwq of interest + * @bwh: hash head as returned by busy_worker_head() + * @work: work to find worker for + * + * Find a worker which is executing @work on @gcwq. @bwh should be + * the hash head obtained by calling busy_worker_head() with the same + * work. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + * + * RETURNS: + * Pointer to worker which is executing @work if found, NULL + * otherwise. + */ +static struct worker *__find_worker_executing_work(struct global_cwq *gcwq, + struct hlist_head *bwh, + struct work_struct *work) +{ + struct worker *worker; + struct hlist_node *tmp; + + hlist_for_each_entry(worker, tmp, bwh, hentry) + if (worker->current_work == work) + return worker; + return NULL; +} + +/** + * find_worker_executing_work - find worker which is executing a work + * @gcwq: gcwq of interest + * @work: work to find worker for + * + * Find a worker which is executing @work on @gcwq. This function is + * identical to __find_worker_executing_work() except that this + * function calculates @bwh itself. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + * + * RETURNS: + * Pointer to worker which is executing @work if found, NULL + * otherwise. + */ +static struct worker *find_worker_executing_work(struct global_cwq *gcwq, + struct work_struct *work) +{ + return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work), + work); +} + +/** + * gcwq_determine_ins_pos - find insertion position + * @gcwq: gcwq of interest + * @cwq: cwq a work is being queued for + * + * A work for @cwq is about to be queued on @gcwq, determine insertion + * position for the work. If @cwq is for HIGHPRI wq, the work is + * queued at the head of the queue but in FIFO order with respect to + * other HIGHPRI works; otherwise, at the end of the queue. This + * function also sets GCWQ_HIGHPRI_PENDING flag to hint @gcwq that + * there are HIGHPRI works pending. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + * + * RETURNS: + * Pointer to inserstion position. + */ +static inline struct list_head *gcwq_determine_ins_pos(struct global_cwq *gcwq, + struct cpu_workqueue_struct *cwq) +{ + struct work_struct *twork; + + if (likely(!(cwq->wq->flags & WQ_HIGHPRI))) + return &gcwq->worklist; + + list_for_each_entry(twork, &gcwq->worklist, entry) { + struct cpu_workqueue_struct *tcwq = get_work_cwq(twork); + + if (!(tcwq->wq->flags & WQ_HIGHPRI)) + break; + } + + gcwq->flags |= GCWQ_HIGHPRI_PENDING; + return &twork->entry; +} + +/** + * insert_work - insert a work into gcwq + * @cwq: cwq @work belongs to + * @work: work to insert + * @head: insertion point + * @extra_flags: extra WORK_STRUCT_* flags to set + * + * Insert @work which belongs to @cwq into @gcwq after @head. + * @extra_flags is or'd to work_struct flags. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + */ +static void insert_work(struct cpu_workqueue_struct *cwq, + struct work_struct *work, struct list_head *head, + unsigned int extra_flags) +{ + struct global_cwq *gcwq = cwq->gcwq; + + /* we own @work, set data and link */ + set_work_cwq(work, cwq, extra_flags); + + /* + * Ensure that we get the right work->data if we see the + * result of list_add() below, see try_to_grab_pending(). + */ + smp_wmb(); + + list_add_tail(&work->entry, head); + + /* + * Ensure either worker_sched_deactivated() sees the above + * list_add_tail() or we see zero nr_running to avoid workers + * lying around lazily while there are works to be processed. + */ + smp_mb(); + + if (__need_more_worker(gcwq)) + wake_up_worker(gcwq); +} + +/* + * Test whether @work is being queued from another work executing on the + * same workqueue. This is rather expensive and should only be used from + * cold paths. + */ +static bool is_chained_work(struct workqueue_struct *wq) +{ + unsigned long flags; + unsigned int cpu; + + for_each_gcwq_cpu(cpu) { + struct global_cwq *gcwq = get_gcwq(cpu); + struct worker *worker; + struct hlist_node *pos; + int i; + + spin_lock_irqsave(&gcwq->lock, flags); + for_each_busy_worker(worker, i, pos, gcwq) { + if (worker->task != current) + continue; + spin_unlock_irqrestore(&gcwq->lock, flags); + /* + * I'm @worker, no locking necessary. See if @work + * is headed to the same workqueue. + */ + return worker->current_cwq->wq == wq; + } + spin_unlock_irqrestore(&gcwq->lock, flags); + } + return false; +} + +static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, + struct work_struct *work) +{ + struct global_cwq *gcwq; + struct cpu_workqueue_struct *cwq; + struct list_head *worklist; + unsigned int work_flags; + unsigned long flags; + + debug_work_activate(work); + + /* if dying, only works from the same workqueue are allowed */ + if (unlikely(wq->flags & WQ_DYING) && + WARN_ON_ONCE(!is_chained_work(wq))) + return; + + /* determine gcwq to use */ + if (!(wq->flags & WQ_UNBOUND)) { + struct global_cwq *last_gcwq; + + if (unlikely(cpu == WORK_CPU_UNBOUND)) + cpu = raw_smp_processor_id(); + + /* + * It's multi cpu. If @wq is non-reentrant and @work + * was previously on a different cpu, it might still + * be running there, in which case the work needs to + * be queued on that cpu to guarantee non-reentrance. + */ + gcwq = get_gcwq(cpu); + if (wq->flags & WQ_NON_REENTRANT && + (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) { + struct worker *worker; + + spin_lock_irqsave(&last_gcwq->lock, flags); + + worker = find_worker_executing_work(last_gcwq, work); + + if (worker && worker->current_cwq->wq == wq) + gcwq = last_gcwq; + else { + /* meh... not running there, queue here */ + spin_unlock_irqrestore(&last_gcwq->lock, flags); + spin_lock_irqsave(&gcwq->lock, flags); + } + } else + spin_lock_irqsave(&gcwq->lock, flags); + } else { + gcwq = get_gcwq(WORK_CPU_UNBOUND); + spin_lock_irqsave(&gcwq->lock, flags); + } + + /* gcwq determined, get cwq and queue */ + cwq = get_cwq(gcwq->cpu, wq); + trace_workqueue_queue_work(cpu, cwq, work); + + BUG_ON(!list_empty(&work->entry)); + + cwq->nr_in_flight[cwq->work_color]++; + work_flags = work_color_to_flags(cwq->work_color); + + if (likely(cwq->nr_active < cwq->max_active)) { + trace_workqueue_activate_work(work); + cwq->nr_active++; + worklist = gcwq_determine_ins_pos(gcwq, cwq); + } else { + work_flags |= WORK_STRUCT_DELAYED; + worklist = &cwq->delayed_works; + } + + insert_work(cwq, work, worklist, work_flags); + + spin_unlock_irqrestore(&gcwq->lock, flags); +} + +/** + * queue_work - queue work on a workqueue + * @wq: workqueue to use + * @work: work to queue + * + * Returns 0 if @work was already on a queue, non-zero otherwise. + * + * We queue the work to the CPU on which it was submitted, but if the CPU dies + * it can be processed by another CPU. + */ +int queue_work(struct workqueue_struct *wq, struct work_struct *work) +{ + int ret; + + ret = queue_work_on(get_cpu(), wq, work); + put_cpu(); + + return ret; +} +EXPORT_SYMBOL_GPL(queue_work); + +/** + * queue_work_on - queue work on specific cpu + * @cpu: CPU number to execute work on + * @wq: workqueue to use + * @work: work to queue + * + * Returns 0 if @work was already on a queue, non-zero otherwise. + * + * We queue the work to a specific CPU, the caller must ensure it + * can't go away. + */ +int +queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work) +{ + int ret = 0; + + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { + __queue_work(cpu, wq, work); + ret = 1; + } + return ret; +} +EXPORT_SYMBOL_GPL(queue_work_on); + +static void delayed_work_timer_fn(unsigned long __data) +{ + struct delayed_work *dwork = (struct delayed_work *)__data; + struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work); + + __queue_work(smp_processor_id(), cwq->wq, &dwork->work); +} + +/** + * queue_delayed_work - queue work on a workqueue after delay + * @wq: workqueue to use + * @dwork: delayable work to queue + * @delay: number of jiffies to wait before queueing + * + * Returns 0 if @work was already on a queue, non-zero otherwise. + */ +int queue_delayed_work(struct workqueue_struct *wq, + struct delayed_work *dwork, unsigned long delay) +{ + if (delay == 0) + return queue_work(wq, &dwork->work); + + return queue_delayed_work_on(-1, wq, dwork, delay); +} +EXPORT_SYMBOL_GPL(queue_delayed_work); + +/** + * queue_delayed_work_on - queue work on specific CPU after delay + * @cpu: CPU number to execute work on + * @wq: workqueue to use + * @dwork: work to queue + * @delay: number of jiffies to wait before queueing + * + * Returns 0 if @work was already on a queue, non-zero otherwise. + */ +int queue_delayed_work_on(int cpu, struct workqueue_struct *wq, + struct delayed_work *dwork, unsigned long delay) +{ + int ret = 0; + struct timer_list *timer = &dwork->timer; + struct work_struct *work = &dwork->work; + + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { + unsigned int lcpu; + + BUG_ON(timer_pending(timer)); + BUG_ON(!list_empty(&work->entry)); + + timer_stats_timer_set_start_info(&dwork->timer); + + /* + * This stores cwq for the moment, for the timer_fn. + * Note that the work's gcwq is preserved to allow + * reentrance detection for delayed works. + */ + if (!(wq->flags & WQ_UNBOUND)) { + struct global_cwq *gcwq = get_work_gcwq(work); + + if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND) + lcpu = gcwq->cpu; + else + lcpu = raw_smp_processor_id(); + } else + lcpu = WORK_CPU_UNBOUND; + + set_work_cwq(work, get_cwq(lcpu, wq), 0); + + timer->expires = jiffies + delay; + timer->data = (unsigned long)dwork; + timer->function = delayed_work_timer_fn; + + if (unlikely(cpu >= 0)) + add_timer_on(timer, cpu); + else + add_timer(timer); + ret = 1; + } + return ret; +} +EXPORT_SYMBOL_GPL(queue_delayed_work_on); + +/** + * worker_enter_idle - enter idle state + * @worker: worker which is entering idle state + * + * @worker is entering idle state. Update stats and idle timer if + * necessary. + * + * LOCKING: + * spin_lock_irq(gcwq->lock). + */ +static void worker_enter_idle(struct worker *worker) +{ + struct global_cwq *gcwq = worker->gcwq; + + BUG_ON(worker->flags & WORKER_IDLE); + BUG_ON(!list_empty(&worker->entry) && + (worker->hentry.next || worker->hentry.pprev)); + + /* can't use worker_set_flags(), also called from start_worker() */ + worker->flags |= WORKER_IDLE; + gcwq->nr_idle++; + worker->last_active = jiffies; + + /* idle_list is LIFO */ + list_add(&worker->entry, &gcwq->idle_list); + + if (likely(!(worker->flags & WORKER_ROGUE))) { + if (too_many_workers(gcwq) && !timer_pending(&gcwq->idle_timer)) + mod_timer(&gcwq->idle_timer, + jiffies + IDLE_WORKER_TIMEOUT); + } else + wake_up_all(&gcwq->trustee_wait); + + /* + * Sanity check nr_running. Because trustee releases gcwq->lock + * between setting %WORKER_ROGUE and zapping nr_running, the + * warning may trigger spuriously. Check iff trustee is idle. + */ + WARN_ON_ONCE(gcwq->trustee_state == TRUSTEE_DONE && + gcwq->nr_workers == gcwq->nr_idle && + atomic_read(get_gcwq_nr_running(gcwq->cpu))); +} + +/** + * worker_leave_idle - leave idle state + * @worker: worker which is leaving idle state + * + * @worker is leaving idle state. Update stats. + * + * LOCKING: + * spin_lock_irq(gcwq->lock). + */ +static void worker_leave_idle(struct worker *worker) +{ + struct global_cwq *gcwq = worker->gcwq; + + BUG_ON(!(worker->flags & WORKER_IDLE)); + worker_clr_flags(worker, WORKER_IDLE); + gcwq->nr_idle--; + list_del_init(&worker->entry); +} + +/** + * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq + * @worker: self + * + * Works which are scheduled while the cpu is online must at least be + * scheduled to a worker which is bound to the cpu so that if they are + * flushed from cpu callbacks while cpu is going down, they are + * guaranteed to execute on the cpu. + * + * This function is to be used by rogue workers and rescuers to bind + * themselves to the target cpu and may race with cpu going down or + * coming online. kthread_bind() can't be used because it may put the + * worker to already dead cpu and set_cpus_allowed_ptr() can't be used + * verbatim as it's best effort and blocking and gcwq may be + * [dis]associated in the meantime. + * + * This function tries set_cpus_allowed() and locks gcwq and verifies + * the binding against GCWQ_DISASSOCIATED which is set during + * CPU_DYING and cleared during CPU_ONLINE, so if the worker enters + * idle state or fetches works without dropping lock, it can guarantee + * the scheduling requirement described in the first paragraph. + * + * CONTEXT: + * Might sleep. Called without any lock but returns with gcwq->lock + * held. + * + * RETURNS: + * %true if the associated gcwq is online (@worker is successfully + * bound), %false if offline. + */ +static bool worker_maybe_bind_and_lock(struct worker *worker) +__acquires(&gcwq->lock) +{ + struct global_cwq *gcwq = worker->gcwq; + struct task_struct *task = worker->task; + + while (true) { + /* + * The following call may fail, succeed or succeed + * without actually migrating the task to the cpu if + * it races with cpu hotunplug operation. Verify + * against GCWQ_DISASSOCIATED. + */ + if (!(gcwq->flags & GCWQ_DISASSOCIATED)) + set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu)); + + spin_lock_irq(&gcwq->lock); + if (gcwq->flags & GCWQ_DISASSOCIATED) + return false; + if (task_cpu(task) == gcwq->cpu && + cpumask_equal(¤t->cpus_allowed, + get_cpu_mask(gcwq->cpu))) + return true; + spin_unlock_irq(&gcwq->lock); + + /* + * We've raced with CPU hot[un]plug. Give it a breather + * and retry migration. cond_resched() is required here; + * otherwise, we might deadlock against cpu_stop trying to + * bring down the CPU on non-preemptive kernel. + */ + cpu_relax(); + cond_resched(); + } +} + +/* + * Function for worker->rebind_work used to rebind rogue busy workers + * to the associated cpu which is coming back online. This is + * scheduled by cpu up but can race with other cpu hotplug operations + * and may be executed twice without intervening cpu down. + */ +static void worker_rebind_fn(struct work_struct *work) +{ + struct worker *worker = container_of(work, struct worker, rebind_work); + struct global_cwq *gcwq = worker->gcwq; + + if (worker_maybe_bind_and_lock(worker)) + worker_clr_flags(worker, WORKER_REBIND); + + spin_unlock_irq(&gcwq->lock); +} + +static struct worker *alloc_worker(void) +{ + struct worker *worker; + + worker = kzalloc(sizeof(*worker), GFP_KERNEL); + if (worker) { + INIT_LIST_HEAD(&worker->entry); + INIT_LIST_HEAD(&worker->scheduled); + INIT_WORK(&worker->rebind_work, worker_rebind_fn); + /* on creation a worker is in !idle && prep state */ + worker->flags = WORKER_PREP; + } + return worker; +} + +/** + * create_worker - create a new workqueue worker + * @gcwq: gcwq the new worker will belong to + * @bind: whether to set affinity to @cpu or not + * + * Create a new worker which is bound to @gcwq. The returned worker + * can be started by calling start_worker() or destroyed using + * destroy_worker(). + * + * CONTEXT: + * Might sleep. Does GFP_KERNEL allocations. + * + * RETURNS: + * Pointer to the newly created worker. + */ +static struct worker *create_worker(struct global_cwq *gcwq, bool bind) +{ + bool on_unbound_cpu = gcwq->cpu == WORK_CPU_UNBOUND; + struct worker *worker = NULL; + int id = -1; + + spin_lock_irq(&gcwq->lock); + while (ida_get_new(&gcwq->worker_ida, &id)) { + spin_unlock_irq(&gcwq->lock); + if (!ida_pre_get(&gcwq->worker_ida, GFP_KERNEL)) + goto fail; + spin_lock_irq(&gcwq->lock); + } + spin_unlock_irq(&gcwq->lock); + + worker = alloc_worker(); + if (!worker) + goto fail; + + worker->gcwq = gcwq; + worker->id = id; + + if (!on_unbound_cpu) + worker->task = kthread_create_on_node(worker_thread, + worker, + cpu_to_node(gcwq->cpu), + "kworker/%u:%d", gcwq->cpu, id); + else + worker->task = kthread_create(worker_thread, worker, + "kworker/u:%d", id); + if (IS_ERR(worker->task)) + goto fail; + + /* + * A rogue worker will become a regular one if CPU comes + * online later on. Make sure every worker has + * PF_THREAD_BOUND set. + */ + if (bind && !on_unbound_cpu) + kthread_bind(worker->task, gcwq->cpu); + else { + worker->task->flags |= PF_THREAD_BOUND; + if (on_unbound_cpu) + worker->flags |= WORKER_UNBOUND; + } + + return worker; +fail: + if (id >= 0) { + spin_lock_irq(&gcwq->lock); + ida_remove(&gcwq->worker_ida, id); + spin_unlock_irq(&gcwq->lock); + } + kfree(worker); + return NULL; +} + +/** + * start_worker - start a newly created worker + * @worker: worker to start + * + * Make the gcwq aware of @worker and start it. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + */ +static void start_worker(struct worker *worker) +{ + worker->flags |= WORKER_STARTED; + worker->gcwq->nr_workers++; + worker_enter_idle(worker); + wake_up_process(worker->task); +} + +/** + * destroy_worker - destroy a workqueue worker + * @worker: worker to be destroyed + * + * Destroy @worker and adjust @gcwq stats accordingly. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) which is released and regrabbed. + */ +static void destroy_worker(struct worker *worker) +{ + struct global_cwq *gcwq = worker->gcwq; + int id = worker->id; + + /* sanity check frenzy */ + BUG_ON(worker->current_work); + BUG_ON(!list_empty(&worker->scheduled)); + + if (worker->flags & WORKER_STARTED) + gcwq->nr_workers--; + if (worker->flags & WORKER_IDLE) + gcwq->nr_idle--; + + list_del_init(&worker->entry); + worker->flags |= WORKER_DIE; + + spin_unlock_irq(&gcwq->lock); + + kthread_stop(worker->task); + kfree(worker); + + spin_lock_irq(&gcwq->lock); + ida_remove(&gcwq->worker_ida, id); +} + +static void idle_worker_timeout(unsigned long __gcwq) +{ + struct global_cwq *gcwq = (void *)__gcwq; + + spin_lock_irq(&gcwq->lock); + + if (too_many_workers(gcwq)) { + struct worker *worker; + unsigned long expires; + + /* idle_list is kept in LIFO order, check the last one */ + worker = list_entry(gcwq->idle_list.prev, struct worker, entry); + expires = worker->last_active + IDLE_WORKER_TIMEOUT; + + if (time_before(jiffies, expires)) + mod_timer(&gcwq->idle_timer, expires); + else { + /* it's been idle for too long, wake up manager */ + gcwq->flags |= GCWQ_MANAGE_WORKERS; + wake_up_worker(gcwq); + } + } + + spin_unlock_irq(&gcwq->lock); +} + +static bool send_mayday(struct work_struct *work) +{ + struct cpu_workqueue_struct *cwq = get_work_cwq(work); + struct workqueue_struct *wq = cwq->wq; + unsigned int cpu; + + if (!(wq->flags & WQ_RESCUER)) + return false; + + /* mayday mayday mayday */ + cpu = cwq->gcwq->cpu; + /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */ + if (cpu == WORK_CPU_UNBOUND) + cpu = 0; + if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask)) + wake_up_process(wq->rescuer->task); + return true; +} + +static void gcwq_mayday_timeout(unsigned long __gcwq) +{ + struct global_cwq *gcwq = (void *)__gcwq; + struct work_struct *work; + + spin_lock_irq(&gcwq->lock); + + if (need_to_create_worker(gcwq)) { + /* + * We've been trying to create a new worker but + * haven't been successful. We might be hitting an + * allocation deadlock. Send distress signals to + * rescuers. + */ + list_for_each_entry(work, &gcwq->worklist, entry) + send_mayday(work); + } + + spin_unlock_irq(&gcwq->lock); + + mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INTERVAL); +} + +/** + * maybe_create_worker - create a new worker if necessary + * @gcwq: gcwq to create a new worker for + * + * Create a new worker for @gcwq if necessary. @gcwq is guaranteed to + * have at least one idle worker on return from this function. If + * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is + * sent to all rescuers with works scheduled on @gcwq to resolve + * possible allocation deadlock. + * + * On return, need_to_create_worker() is guaranteed to be false and + * may_start_working() true. + * + * LOCKING: + * spin_lock_irq(gcwq->lock) which may be released and regrabbed + * multiple times. Does GFP_KERNEL allocations. Called only from + * manager. + * + * RETURNS: + * false if no action was taken and gcwq->lock stayed locked, true + * otherwise. + */ +static bool maybe_create_worker(struct global_cwq *gcwq) +__releases(&gcwq->lock) +__acquires(&gcwq->lock) +{ + if (!need_to_create_worker(gcwq)) + return false; +restart: + spin_unlock_irq(&gcwq->lock); + + /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */ + mod_timer(&gcwq->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT); + + while (true) { + struct worker *worker; + + worker = create_worker(gcwq, true); + if (worker) { + del_timer_sync(&gcwq->mayday_timer); + spin_lock_irq(&gcwq->lock); + start_worker(worker); + BUG_ON(need_to_create_worker(gcwq)); + return true; + } + + if (!need_to_create_worker(gcwq)) + break; + + __set_current_state(TASK_INTERRUPTIBLE); + schedule_timeout(CREATE_COOLDOWN); + + if (!need_to_create_worker(gcwq)) + break; + } + + del_timer_sync(&gcwq->mayday_timer); + spin_lock_irq(&gcwq->lock); + if (need_to_create_worker(gcwq)) + goto restart; + return true; +} + +/** + * maybe_destroy_worker - destroy workers which have been idle for a while + * @gcwq: gcwq to destroy workers for + * + * Destroy @gcwq workers which have been idle for longer than + * IDLE_WORKER_TIMEOUT. + * + * LOCKING: + * spin_lock_irq(gcwq->lock) which may be released and regrabbed + * multiple times. Called only from manager. + * + * RETURNS: + * false if no action was taken and gcwq->lock stayed locked, true + * otherwise. + */ +static bool maybe_destroy_workers(struct global_cwq *gcwq) +{ + bool ret = false; + + while (too_many_workers(gcwq)) { + struct worker *worker; + unsigned long expires; + + worker = list_entry(gcwq->idle_list.prev, struct worker, entry); + expires = worker->last_active + IDLE_WORKER_TIMEOUT; + + if (time_before(jiffies, expires)) { + mod_timer(&gcwq->idle_timer, expires); + break; + } + + destroy_worker(worker); + ret = true; + } + + return ret; +} + +/** + * manage_workers - manage worker pool + * @worker: self + * + * Assume the manager role and manage gcwq worker pool @worker belongs + * to. At any given time, there can be only zero or one manager per + * gcwq. The exclusion is handled automatically by this function. + * + * The caller can safely start processing works on false return. On + * true return, it's guaranteed that need_to_create_worker() is false + * and may_start_working() is true. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) which may be released and regrabbed + * multiple times. Does GFP_KERNEL allocations. + * + * RETURNS: + * false if no action was taken and gcwq->lock stayed locked, true if + * some action was taken. + */ +static bool manage_workers(struct worker *worker) +{ + struct global_cwq *gcwq = worker->gcwq; + bool ret = false; + + if (gcwq->flags & GCWQ_MANAGING_WORKERS) + return ret; + + gcwq->flags &= ~GCWQ_MANAGE_WORKERS; + gcwq->flags |= GCWQ_MANAGING_WORKERS; + + /* + * Destroy and then create so that may_start_working() is true + * on return. + */ + ret |= maybe_destroy_workers(gcwq); + ret |= maybe_create_worker(gcwq); + + gcwq->flags &= ~GCWQ_MANAGING_WORKERS; + + /* + * The trustee might be waiting to take over the manager + * position, tell it we're done. + */ + if (unlikely(gcwq->trustee)) + wake_up_all(&gcwq->trustee_wait); + + return ret; +} + +/** + * move_linked_works - move linked works to a list + * @work: start of series of works to be scheduled + * @head: target list to append @work to + * @nextp: out paramter for nested worklist walking + * + * Schedule linked works starting from @work to @head. Work series to + * be scheduled starts at @work and includes any consecutive work with + * WORK_STRUCT_LINKED set in its predecessor. + * + * If @nextp is not NULL, it's updated to point to the next work of + * the last scheduled work. This allows move_linked_works() to be + * nested inside outer list_for_each_entry_safe(). + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + */ +static void move_linked_works(struct work_struct *work, struct list_head *head, + struct work_struct **nextp) +{ + struct work_struct *n; + + /* + * Linked worklist will always end before the end of the list, + * use NULL for list head. + */ + list_for_each_entry_safe_from(work, n, NULL, entry) { + list_move_tail(&work->entry, head); + if (!(*work_data_bits(work) & WORK_STRUCT_LINKED)) + break; + } + + /* + * If we're already inside safe list traversal and have moved + * multiple works to the scheduled queue, the next position + * needs to be updated. + */ + if (nextp) + *nextp = n; +} + +static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) +{ + struct work_struct *work = list_first_entry(&cwq->delayed_works, + struct work_struct, entry); + struct list_head *pos = gcwq_determine_ins_pos(cwq->gcwq, cwq); + + trace_workqueue_activate_work(work); + move_linked_works(work, pos, NULL); + __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work)); + cwq->nr_active++; +} + +/** + * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight + * @cwq: cwq of interest + * @color: color of work which left the queue + * @delayed: for a delayed work + * + * A work either has completed or is removed from pending queue, + * decrement nr_in_flight of its cwq and handle workqueue flushing. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + */ +static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color, + bool delayed) +{ + /* ignore uncolored works */ + if (color == WORK_NO_COLOR) + return; + + cwq->nr_in_flight[color]--; + + if (!delayed) { + cwq->nr_active--; + if (!list_empty(&cwq->delayed_works)) { + /* one down, submit a delayed one */ + if (cwq->nr_active < cwq->max_active) + cwq_activate_first_delayed(cwq); + } + } + + /* is flush in progress and are we at the flushing tip? */ + if (likely(cwq->flush_color != color)) + return; + + /* are there still in-flight works? */ + if (cwq->nr_in_flight[color]) + return; + + /* this cwq is done, clear flush_color */ + cwq->flush_color = -1; + + /* + * If this was the last cwq, wake up the first flusher. It + * will handle the rest. + */ + if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush)) + complete(&cwq->wq->first_flusher->done); +} + +/** + * process_one_work - process single work + * @worker: self + * @work: work to process + * + * Process @work. This function contains all the logics necessary to + * process a single work including synchronization against and + * interaction with other workers on the same cpu, queueing and + * flushing. As long as context requirement is met, any worker can + * call this function to process a work. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) which is released and regrabbed. + */ +static void process_one_work(struct worker *worker, struct work_struct *work) +__releases(&gcwq->lock) +__acquires(&gcwq->lock) +{ + struct cpu_workqueue_struct *cwq = get_work_cwq(work); + struct global_cwq *gcwq = cwq->gcwq; + struct hlist_head *bwh = busy_worker_head(gcwq, work); + bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE; + work_func_t f = work->func; + int work_color; + struct worker *collision; +#ifdef CONFIG_LOCKDEP + /* + * It is permissible to free the struct work_struct from + * inside the function that is called from it, this we need to + * take into account for lockdep too. To avoid bogus "held + * lock freed" warnings as well as problems when looking into + * work->lockdep_map, make a copy and use that here. + */ + struct lockdep_map lockdep_map = work->lockdep_map; +#endif + /* + * A single work shouldn't be executed concurrently by + * multiple workers on a single cpu. Check whether anyone is + * already processing the work. If so, defer the work to the + * currently executing one. + */ + collision = __find_worker_executing_work(gcwq, bwh, work); + if (unlikely(collision)) { + move_linked_works(work, &collision->scheduled, NULL); + return; + } + + /* claim and process */ + debug_work_deactivate(work); + hlist_add_head(&worker->hentry, bwh); + worker->current_work = work; + worker->current_cwq = cwq; + work_color = get_work_color(work); + + /* record the current cpu number in the work data and dequeue */ + set_work_cpu(work, gcwq->cpu); + list_del_init(&work->entry); + + /* + * If HIGHPRI_PENDING, check the next work, and, if HIGHPRI, + * wake up another worker; otherwise, clear HIGHPRI_PENDING. + */ + if (unlikely(gcwq->flags & GCWQ_HIGHPRI_PENDING)) { + struct work_struct *nwork = list_first_entry(&gcwq->worklist, + struct work_struct, entry); + + if (!list_empty(&gcwq->worklist) && + get_work_cwq(nwork)->wq->flags & WQ_HIGHPRI) + wake_up_worker(gcwq); + else + gcwq->flags &= ~GCWQ_HIGHPRI_PENDING; + } + + /* + * CPU intensive works don't participate in concurrency + * management. They're the scheduler's responsibility. + */ + if (unlikely(cpu_intensive)) + worker_set_flags(worker, WORKER_CPU_INTENSIVE, true); + + spin_unlock_irq(&gcwq->lock); + + work_clear_pending(work); + lock_map_acquire_read(&cwq->wq->lockdep_map); + lock_map_acquire(&lockdep_map); + trace_workqueue_execute_start(work); + f(work); + /* + * While we must be careful to not use "work" after this, the trace + * point will only record its address. + */ + trace_workqueue_execute_end(work); + lock_map_release(&lockdep_map); + lock_map_release(&cwq->wq->lockdep_map); + + if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { + printk(KERN_ERR "BUG: workqueue leaked lock or atomic: " + "%s/0x%08x/%d\n", + current->comm, preempt_count(), task_pid_nr(current)); + printk(KERN_ERR " last function: "); + print_symbol("%s\n", (unsigned long)f); + debug_show_held_locks(current); + dump_stack(); + } + + spin_lock_irq(&gcwq->lock); + + /* clear cpu intensive status */ + if (unlikely(cpu_intensive)) + worker_clr_flags(worker, WORKER_CPU_INTENSIVE); + + /* we're done with it, release */ + hlist_del_init(&worker->hentry); + worker->current_work = NULL; + worker->current_cwq = NULL; + cwq_dec_nr_in_flight(cwq, work_color, false); +} + +/** + * process_scheduled_works - process scheduled works + * @worker: self + * + * Process all scheduled works. Please note that the scheduled list + * may change while processing a work, so this function repeatedly + * fetches a work from the top and executes it. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) which may be released and regrabbed + * multiple times. + */ +static void process_scheduled_works(struct worker *worker) +{ + while (!list_empty(&worker->scheduled)) { + struct work_struct *work = list_first_entry(&worker->scheduled, + struct work_struct, entry); + process_one_work(worker, work); + } +} + +/** + * worker_thread - the worker thread function + * @__worker: self + * + * The gcwq worker thread function. There's a single dynamic pool of + * these per each cpu. These workers process all works regardless of + * their specific target workqueue. The only exception is works which + * belong to workqueues with a rescuer which will be explained in + * rescuer_thread(). + */ +static int worker_thread(void *__worker) +{ + struct worker *worker = __worker; + struct global_cwq *gcwq = worker->gcwq; + + /* tell the scheduler that this is a workqueue worker */ + worker->task->flags |= PF_WQ_WORKER; +woke_up: + spin_lock_irq(&gcwq->lock); + + /* DIE can be set only while we're idle, checking here is enough */ + if (worker->flags & WORKER_DIE) { + spin_unlock_irq(&gcwq->lock); + worker->task->flags &= ~PF_WQ_WORKER; + return 0; + } + + worker_leave_idle(worker); +recheck: + /* no more worker necessary? */ + if (!need_more_worker(gcwq)) + goto sleep; + + /* do we need to manage? */ + if (unlikely(!may_start_working(gcwq)) && manage_workers(worker)) + goto recheck; + + /* + * ->scheduled list can only be filled while a worker is + * preparing to process a work or actually processing it. + * Make sure nobody diddled with it while I was sleeping. + */ + BUG_ON(!list_empty(&worker->scheduled)); + + /* + * When control reaches this point, we're guaranteed to have + * at least one idle worker or that someone else has already + * assumed the manager role. + */ + worker_clr_flags(worker, WORKER_PREP); + + do { + struct work_struct *work = + list_first_entry(&gcwq->worklist, + struct work_struct, entry); + + if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) { + /* optimization path, not strictly necessary */ + process_one_work(worker, work); + if (unlikely(!list_empty(&worker->scheduled))) + process_scheduled_works(worker); + } else { + move_linked_works(work, &worker->scheduled, NULL); + process_scheduled_works(worker); + } + } while (keep_working(gcwq)); + + worker_set_flags(worker, WORKER_PREP, false); +sleep: + if (unlikely(need_to_manage_workers(gcwq)) && manage_workers(worker)) + goto recheck; + + /* + * gcwq->lock is held and there's no work to process and no + * need to manage, sleep. Workers are woken up only while + * holding gcwq->lock or from local cpu, so setting the + * current state before releasing gcwq->lock is enough to + * prevent losing any event. + */ + worker_enter_idle(worker); + __set_current_state(TASK_INTERRUPTIBLE); + spin_unlock_irq(&gcwq->lock); + schedule(); + goto woke_up; +} + +/** + * rescuer_thread - the rescuer thread function + * @__wq: the associated workqueue + * + * Workqueue rescuer thread function. There's one rescuer for each + * workqueue which has WQ_RESCUER set. + * + * Regular work processing on a gcwq may block trying to create a new + * worker which uses GFP_KERNEL allocation which has slight chance of + * developing into deadlock if some works currently on the same queue + * need to be processed to satisfy the GFP_KERNEL allocation. This is + * the problem rescuer solves. + * + * When such condition is possible, the gcwq summons rescuers of all + * workqueues which have works queued on the gcwq and let them process + * those works so that forward progress can be guaranteed. + * + * This should happen rarely. + */ +static int rescuer_thread(void *__wq) +{ + struct workqueue_struct *wq = __wq; + struct worker *rescuer = wq->rescuer; + struct list_head *scheduled = &rescuer->scheduled; + bool is_unbound = wq->flags & WQ_UNBOUND; + unsigned int cpu; + + set_user_nice(current, RESCUER_NICE_LEVEL); +repeat: + set_current_state(TASK_INTERRUPTIBLE); + + if (kthread_should_stop()) + return 0; + + /* + * See whether any cpu is asking for help. Unbounded + * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND. + */ + for_each_mayday_cpu(cpu, wq->mayday_mask) { + unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu; + struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq); + struct global_cwq *gcwq = cwq->gcwq; + struct work_struct *work, *n; + + __set_current_state(TASK_RUNNING); + mayday_clear_cpu(cpu, wq->mayday_mask); + + /* migrate to the target cpu if possible */ + rescuer->gcwq = gcwq; + worker_maybe_bind_and_lock(rescuer); + + /* + * Slurp in all works issued via this workqueue and + * process'em. + */ + BUG_ON(!list_empty(&rescuer->scheduled)); + list_for_each_entry_safe(work, n, &gcwq->worklist, entry) + if (get_work_cwq(work) == cwq) + move_linked_works(work, scheduled, &n); + + process_scheduled_works(rescuer); + + /* + * Leave this gcwq. If keep_working() is %true, notify a + * regular worker; otherwise, we end up with 0 concurrency + * and stalling the execution. + */ + if (keep_working(gcwq)) + wake_up_worker(gcwq); + + spin_unlock_irq(&gcwq->lock); + } + + schedule(); + goto repeat; +} + +struct wq_barrier { + struct work_struct work; + struct completion done; +}; + +static void wq_barrier_func(struct work_struct *work) +{ + struct wq_barrier *barr = container_of(work, struct wq_barrier, work); + complete(&barr->done); +} + +/** + * insert_wq_barrier - insert a barrier work + * @cwq: cwq to insert barrier into + * @barr: wq_barrier to insert + * @target: target work to attach @barr to + * @worker: worker currently executing @target, NULL if @target is not executing + * + * @barr is linked to @target such that @barr is completed only after + * @target finishes execution. Please note that the ordering + * guarantee is observed only with respect to @target and on the local + * cpu. + * + * Currently, a queued barrier can't be canceled. This is because + * try_to_grab_pending() can't determine whether the work to be + * grabbed is at the head of the queue and thus can't clear LINKED + * flag of the previous work while there must be a valid next work + * after a work with LINKED flag set. + * + * Note that when @worker is non-NULL, @target may be modified + * underneath us, so we can't reliably determine cwq from @target. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock). + */ +static void insert_wq_barrier(struct cpu_workqueue_struct *cwq, + struct wq_barrier *barr, + struct work_struct *target, struct worker *worker) +{ + struct list_head *head; + unsigned int linked = 0; + + /* + * debugobject calls are safe here even with gcwq->lock locked + * as we know for sure that this will not trigger any of the + * checks and call back into the fixup functions where we + * might deadlock. + */ + INIT_WORK_ONSTACK(&barr->work, wq_barrier_func); + __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work)); + init_completion(&barr->done); + + /* + * If @target is currently being executed, schedule the + * barrier to the worker; otherwise, put it after @target. + */ + if (worker) + head = worker->scheduled.next; + else { + unsigned long *bits = work_data_bits(target); + + head = target->entry.next; + /* there can already be other linked works, inherit and set */ + linked = *bits & WORK_STRUCT_LINKED; + __set_bit(WORK_STRUCT_LINKED_BIT, bits); + } + + debug_work_activate(&barr->work); + insert_work(cwq, &barr->work, head, + work_color_to_flags(WORK_NO_COLOR) | linked); +} + +/** + * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing + * @wq: workqueue being flushed + * @flush_color: new flush color, < 0 for no-op + * @work_color: new work color, < 0 for no-op + * + * Prepare cwqs for workqueue flushing. + * + * If @flush_color is non-negative, flush_color on all cwqs should be + * -1. If no cwq has in-flight commands at the specified color, all + * cwq->flush_color's stay at -1 and %false is returned. If any cwq + * has in flight commands, its cwq->flush_color is set to + * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq + * wakeup logic is armed and %true is returned. + * + * The caller should have initialized @wq->first_flusher prior to + * calling this function with non-negative @flush_color. If + * @flush_color is negative, no flush color update is done and %false + * is returned. + * + * If @work_color is non-negative, all cwqs should have the same + * work_color which is previous to @work_color and all will be + * advanced to @work_color. + * + * CONTEXT: + * mutex_lock(wq->flush_mutex). + * + * RETURNS: + * %true if @flush_color >= 0 and there's something to flush. %false + * otherwise. + */ +static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq, + int flush_color, int work_color) +{ + bool wait = false; + unsigned int cpu; + + if (flush_color >= 0) { + BUG_ON(atomic_read(&wq->nr_cwqs_to_flush)); + atomic_set(&wq->nr_cwqs_to_flush, 1); + } + + for_each_cwq_cpu(cpu, wq) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + struct global_cwq *gcwq = cwq->gcwq; + + spin_lock_irq(&gcwq->lock); + + if (flush_color >= 0) { + BUG_ON(cwq->flush_color != -1); + + if (cwq->nr_in_flight[flush_color]) { + cwq->flush_color = flush_color; + atomic_inc(&wq->nr_cwqs_to_flush); + wait = true; + } + } + + if (work_color >= 0) { + BUG_ON(work_color != work_next_color(cwq->work_color)); + cwq->work_color = work_color; + } + + spin_unlock_irq(&gcwq->lock); + } + + if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush)) + complete(&wq->first_flusher->done); + + return wait; +} + +/** + * flush_workqueue - ensure that any scheduled work has run to completion. + * @wq: workqueue to flush + * + * Forces execution of the workqueue and blocks until its completion. + * This is typically used in driver shutdown handlers. + * + * We sleep until all works which were queued on entry have been handled, + * but we are not livelocked by new incoming ones. + */ +void flush_workqueue(struct workqueue_struct *wq) +{ + struct wq_flusher this_flusher = { + .list = LIST_HEAD_INIT(this_flusher.list), + .flush_color = -1, + .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done), + }; + int next_color; + + lock_map_acquire(&wq->lockdep_map); + lock_map_release(&wq->lockdep_map); + + mutex_lock(&wq->flush_mutex); + + /* + * Start-to-wait phase + */ + next_color = work_next_color(wq->work_color); + + if (next_color != wq->flush_color) { + /* + * Color space is not full. The current work_color + * becomes our flush_color and work_color is advanced + * by one. + */ + BUG_ON(!list_empty(&wq->flusher_overflow)); + this_flusher.flush_color = wq->work_color; + wq->work_color = next_color; + + if (!wq->first_flusher) { + /* no flush in progress, become the first flusher */ + BUG_ON(wq->flush_color != this_flusher.flush_color); + + wq->first_flusher = &this_flusher; + + if (!flush_workqueue_prep_cwqs(wq, wq->flush_color, + wq->work_color)) { + /* nothing to flush, done */ + wq->flush_color = next_color; + wq->first_flusher = NULL; + goto out_unlock; + } + } else { + /* wait in queue */ + BUG_ON(wq->flush_color == this_flusher.flush_color); + list_add_tail(&this_flusher.list, &wq->flusher_queue); + flush_workqueue_prep_cwqs(wq, -1, wq->work_color); + } + } else { + /* + * Oops, color space is full, wait on overflow queue. + * The next flush completion will assign us + * flush_color and transfer to flusher_queue. + */ + list_add_tail(&this_flusher.list, &wq->flusher_overflow); + } + + mutex_unlock(&wq->flush_mutex); + + wait_for_completion(&this_flusher.done); + + /* + * Wake-up-and-cascade phase + * + * First flushers are responsible for cascading flushes and + * handling overflow. Non-first flushers can simply return. + */ + if (wq->first_flusher != &this_flusher) + return; + + mutex_lock(&wq->flush_mutex); + + /* we might have raced, check again with mutex held */ + if (wq->first_flusher != &this_flusher) + goto out_unlock; + + wq->first_flusher = NULL; + + BUG_ON(!list_empty(&this_flusher.list)); + BUG_ON(wq->flush_color != this_flusher.flush_color); + + while (true) { + struct wq_flusher *next, *tmp; + + /* complete all the flushers sharing the current flush color */ + list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) { + if (next->flush_color != wq->flush_color) + break; + list_del_init(&next->list); + complete(&next->done); + } + + BUG_ON(!list_empty(&wq->flusher_overflow) && + wq->flush_color != work_next_color(wq->work_color)); + + /* this flush_color is finished, advance by one */ + wq->flush_color = work_next_color(wq->flush_color); + + /* one color has been freed, handle overflow queue */ + if (!list_empty(&wq->flusher_overflow)) { + /* + * Assign the same color to all overflowed + * flushers, advance work_color and append to + * flusher_queue. This is the start-to-wait + * phase for these overflowed flushers. + */ + list_for_each_entry(tmp, &wq->flusher_overflow, list) + tmp->flush_color = wq->work_color; + + wq->work_color = work_next_color(wq->work_color); + + list_splice_tail_init(&wq->flusher_overflow, + &wq->flusher_queue); + flush_workqueue_prep_cwqs(wq, -1, wq->work_color); + } + + if (list_empty(&wq->flusher_queue)) { + BUG_ON(wq->flush_color != wq->work_color); + break; + } + + /* + * Need to flush more colors. Make the next flusher + * the new first flusher and arm cwqs. + */ + BUG_ON(wq->flush_color == wq->work_color); + BUG_ON(wq->flush_color != next->flush_color); + + list_del_init(&next->list); + wq->first_flusher = next; + + if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1)) + break; + + /* + * Meh... this color is already done, clear first + * flusher and repeat cascading. + */ + wq->first_flusher = NULL; + } + +out_unlock: + mutex_unlock(&wq->flush_mutex); +} +EXPORT_SYMBOL_GPL(flush_workqueue); + +static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr, + bool wait_executing) +{ + struct worker *worker = NULL; + struct global_cwq *gcwq; + struct cpu_workqueue_struct *cwq; + + might_sleep(); + gcwq = get_work_gcwq(work); + if (!gcwq) + return false; + + spin_lock_irq(&gcwq->lock); + if (!list_empty(&work->entry)) { + /* + * See the comment near try_to_grab_pending()->smp_rmb(). + * If it was re-queued to a different gcwq under us, we + * are not going to wait. + */ + smp_rmb(); + cwq = get_work_cwq(work); + if (unlikely(!cwq || gcwq != cwq->gcwq)) + goto already_gone; + } else if (wait_executing) { + worker = find_worker_executing_work(gcwq, work); + if (!worker) + goto already_gone; + cwq = worker->current_cwq; + } else + goto already_gone; + + insert_wq_barrier(cwq, barr, work, worker); + spin_unlock_irq(&gcwq->lock); + + /* + * If @max_active is 1 or rescuer is in use, flushing another work + * item on the same workqueue may lead to deadlock. Make sure the + * flusher is not running on the same workqueue by verifying write + * access. + */ + if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER) + lock_map_acquire(&cwq->wq->lockdep_map); + else + lock_map_acquire_read(&cwq->wq->lockdep_map); + lock_map_release(&cwq->wq->lockdep_map); + + return true; +already_gone: + spin_unlock_irq(&gcwq->lock); + return false; +} + +/** + * flush_work - wait for a work to finish executing the last queueing instance + * @work: the work to flush + * + * Wait until @work has finished execution. This function considers + * only the last queueing instance of @work. If @work has been + * enqueued across different CPUs on a non-reentrant workqueue or on + * multiple workqueues, @work might still be executing on return on + * some of the CPUs from earlier queueing. + * + * If @work was queued only on a non-reentrant, ordered or unbound + * workqueue, @work is guaranteed to be idle on return if it hasn't + * been requeued since flush started. + * + * RETURNS: + * %true if flush_work() waited for the work to finish execution, + * %false if it was already idle. + */ +bool flush_work(struct work_struct *work) +{ + struct wq_barrier barr; + + if (start_flush_work(work, &barr, true)) { + wait_for_completion(&barr.done); + destroy_work_on_stack(&barr.work); + return true; + } else + return false; +} +EXPORT_SYMBOL_GPL(flush_work); + +static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work) +{ + struct wq_barrier barr; + struct worker *worker; + + spin_lock_irq(&gcwq->lock); + + worker = find_worker_executing_work(gcwq, work); + if (unlikely(worker)) + insert_wq_barrier(worker->current_cwq, &barr, work, worker); + + spin_unlock_irq(&gcwq->lock); + + if (unlikely(worker)) { + wait_for_completion(&barr.done); + destroy_work_on_stack(&barr.work); + return true; + } else + return false; +} + +static bool wait_on_work(struct work_struct *work) +{ + bool ret = false; + int cpu; + + might_sleep(); + + lock_map_acquire(&work->lockdep_map); + lock_map_release(&work->lockdep_map); + + for_each_gcwq_cpu(cpu) + ret |= wait_on_cpu_work(get_gcwq(cpu), work); + return ret; +} + +/** + * flush_work_sync - wait until a work has finished execution + * @work: the work to flush + * + * Wait until @work has finished execution. On return, it's + * guaranteed that all queueing instances of @work which happened + * before this function is called are finished. In other words, if + * @work hasn't been requeued since this function was called, @work is + * guaranteed to be idle on return. + * + * RETURNS: + * %true if flush_work_sync() waited for the work to finish execution, + * %false if it was already idle. + */ +bool flush_work_sync(struct work_struct *work) +{ + struct wq_barrier barr; + bool pending, waited; + + /* we'll wait for executions separately, queue barr only if pending */ + pending = start_flush_work(work, &barr, false); + + /* wait for executions to finish */ + waited = wait_on_work(work); + + /* wait for the pending one */ + if (pending) { + wait_for_completion(&barr.done); + destroy_work_on_stack(&barr.work); + } + + return pending || waited; +} +EXPORT_SYMBOL_GPL(flush_work_sync); + +/* + * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit, + * so this work can't be re-armed in any way. + */ +static int try_to_grab_pending(struct work_struct *work) +{ + struct global_cwq *gcwq; + int ret = -1; + + if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) + return 0; + + /* + * The queueing is in progress, or it is already queued. Try to + * steal it from ->worklist without clearing WORK_STRUCT_PENDING. + */ + gcwq = get_work_gcwq(work); + if (!gcwq) + return ret; + + spin_lock_irq(&gcwq->lock); + if (!list_empty(&work->entry)) { + /* + * This work is queued, but perhaps we locked the wrong gcwq. + * In that case we must see the new value after rmb(), see + * insert_work()->wmb(). + */ + smp_rmb(); + if (gcwq == get_work_gcwq(work)) { + debug_work_deactivate(work); + list_del_init(&work->entry); + cwq_dec_nr_in_flight(get_work_cwq(work), + get_work_color(work), + *work_data_bits(work) & WORK_STRUCT_DELAYED); + ret = 1; + } + } + spin_unlock_irq(&gcwq->lock); + + return ret; +} + +static bool __cancel_work_timer(struct work_struct *work, + struct timer_list* timer) +{ + int ret; + + do { + ret = (timer && likely(del_timer(timer))); + if (!ret) + ret = try_to_grab_pending(work); + wait_on_work(work); + } while (unlikely(ret < 0)); + + clear_work_data(work); + return ret; +} + +/** + * cancel_work_sync - cancel a work and wait for it to finish + * @work: the work to cancel + * + * Cancel @work and wait for its execution to finish. This function + * can be used even if the work re-queues itself or migrates to + * another workqueue. On return from this function, @work is + * guaranteed to be not pending or executing on any CPU. + * + * cancel_work_sync(&delayed_work->work) must not be used for + * delayed_work's. Use cancel_delayed_work_sync() instead. + * + * The caller must ensure that the workqueue on which @work was last + * queued can't be destroyed before this function returns. + * + * RETURNS: + * %true if @work was pending, %false otherwise. + */ +bool cancel_work_sync(struct work_struct *work) +{ + return __cancel_work_timer(work, NULL); +} +EXPORT_SYMBOL_GPL(cancel_work_sync); + +/** + * flush_delayed_work - wait for a dwork to finish executing the last queueing + * @dwork: the delayed work to flush + * + * Delayed timer is cancelled and the pending work is queued for + * immediate execution. Like flush_work(), this function only + * considers the last queueing instance of @dwork. + * + * RETURNS: + * %true if flush_work() waited for the work to finish execution, + * %false if it was already idle. + */ +bool flush_delayed_work(struct delayed_work *dwork) +{ + if (del_timer_sync(&dwork->timer)) + __queue_work(raw_smp_processor_id(), + get_work_cwq(&dwork->work)->wq, &dwork->work); + return flush_work(&dwork->work); +} +EXPORT_SYMBOL(flush_delayed_work); + +/** + * flush_delayed_work_sync - wait for a dwork to finish + * @dwork: the delayed work to flush + * + * Delayed timer is cancelled and the pending work is queued for + * execution immediately. Other than timer handling, its behavior + * is identical to flush_work_sync(). + * + * RETURNS: + * %true if flush_work_sync() waited for the work to finish execution, + * %false if it was already idle. + */ +bool flush_delayed_work_sync(struct delayed_work *dwork) +{ + if (del_timer_sync(&dwork->timer)) + __queue_work(raw_smp_processor_id(), + get_work_cwq(&dwork->work)->wq, &dwork->work); + return flush_work_sync(&dwork->work); +} +EXPORT_SYMBOL(flush_delayed_work_sync); + +/** + * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish + * @dwork: the delayed work cancel + * + * This is cancel_work_sync() for delayed works. + * + * RETURNS: + * %true if @dwork was pending, %false otherwise. + */ +bool cancel_delayed_work_sync(struct delayed_work *dwork) +{ + return __cancel_work_timer(&dwork->work, &dwork->timer); +} +EXPORT_SYMBOL(cancel_delayed_work_sync); + +/** + * schedule_work - put work task in global workqueue + * @work: job to be done + * + * Returns zero if @work was already on the kernel-global workqueue and + * non-zero otherwise. + * + * This puts a job in the kernel-global workqueue if it was not already + * queued and leaves it in the same position on the kernel-global + * workqueue otherwise. + */ +int schedule_work(struct work_struct *work) +{ + return queue_work(system_wq, work); +} +EXPORT_SYMBOL(schedule_work); + +/* + * schedule_work_on - put work task on a specific cpu + * @cpu: cpu to put the work task on + * @work: job to be done + * + * This puts a job on a specific cpu + */ +int schedule_work_on(int cpu, struct work_struct *work) +{ + return queue_work_on(cpu, system_wq, work); +} +EXPORT_SYMBOL(schedule_work_on); + +/** + * schedule_delayed_work - put work task in global workqueue after delay + * @dwork: job to be done + * @delay: number of jiffies to wait or 0 for immediate execution + * + * After waiting for a given time this puts a job in the kernel-global + * workqueue. + */ +int schedule_delayed_work(struct delayed_work *dwork, + unsigned long delay) +{ + return queue_delayed_work(system_wq, dwork, delay); +} +EXPORT_SYMBOL(schedule_delayed_work); + +/** + * schedule_delayed_work_on - queue work in global workqueue on CPU after delay + * @cpu: cpu to use + * @dwork: job to be done + * @delay: number of jiffies to wait + * + * After waiting for a given time this puts a job in the kernel-global + * workqueue on the specified CPU. + */ +int schedule_delayed_work_on(int cpu, + struct delayed_work *dwork, unsigned long delay) +{ + return queue_delayed_work_on(cpu, system_wq, dwork, delay); +} +EXPORT_SYMBOL(schedule_delayed_work_on); + +/** + * schedule_on_each_cpu - execute a function synchronously on each online CPU + * @func: the function to call + * + * schedule_on_each_cpu() executes @func on each online CPU using the + * system workqueue and blocks until all CPUs have completed. + * schedule_on_each_cpu() is very slow. + * + * RETURNS: + * 0 on success, -errno on failure. + */ +int schedule_on_each_cpu(work_func_t func) +{ + int cpu; + struct work_struct __percpu *works; + + works = alloc_percpu(struct work_struct); + if (!works) + return -ENOMEM; + + get_online_cpus(); + + for_each_online_cpu(cpu) { + struct work_struct *work = per_cpu_ptr(works, cpu); + + INIT_WORK(work, func); + schedule_work_on(cpu, work); + } + + for_each_online_cpu(cpu) + flush_work(per_cpu_ptr(works, cpu)); + + put_online_cpus(); + free_percpu(works); + return 0; +} + +/** + * flush_scheduled_work - ensure that any scheduled work has run to completion. + * + * Forces execution of the kernel-global workqueue and blocks until its + * completion. + * + * Think twice before calling this function! It's very easy to get into + * trouble if you don't take great care. Either of the following situations + * will lead to deadlock: + * + * One of the work items currently on the workqueue needs to acquire + * a lock held by your code or its caller. + * + * Your code is running in the context of a work routine. + * + * They will be detected by lockdep when they occur, but the first might not + * occur very often. It depends on what work items are on the workqueue and + * what locks they need, which you have no control over. + * + * In most situations flushing the entire workqueue is overkill; you merely + * need to know that a particular work item isn't queued and isn't running. + * In such cases you should use cancel_delayed_work_sync() or + * cancel_work_sync() instead. + */ +void flush_scheduled_work(void) +{ + flush_workqueue(system_wq); +} +EXPORT_SYMBOL(flush_scheduled_work); + +/** + * execute_in_process_context - reliably execute the routine with user context + * @fn: the function to execute + * @ew: guaranteed storage for the execute work structure (must + * be available when the work executes) + * + * Executes the function immediately if process context is available, + * otherwise schedules the function for delayed execution. + * + * Returns: 0 - function was executed + * 1 - function was scheduled for execution + */ +int execute_in_process_context(work_func_t fn, struct execute_work *ew) +{ + if (!in_interrupt()) { + fn(&ew->work); + return 0; + } + + INIT_WORK(&ew->work, fn); + schedule_work(&ew->work); + + return 1; +} +EXPORT_SYMBOL_GPL(execute_in_process_context); + +int keventd_up(void) +{ + return system_wq != NULL; +} + +static int alloc_cwqs(struct workqueue_struct *wq) +{ + /* + * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS. + * Make sure that the alignment isn't lower than that of + * unsigned long long. + */ + const size_t size = sizeof(struct cpu_workqueue_struct); + const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS, + __alignof__(unsigned long long)); +#ifdef CONFIG_SMP + bool percpu = !(wq->flags & WQ_UNBOUND); +#else + bool percpu = false; +#endif + + if (percpu) + wq->cpu_wq.pcpu = __alloc_percpu(size, align); + else { + void *ptr; + + /* + * Allocate enough room to align cwq and put an extra + * pointer at the end pointing back to the originally + * allocated pointer which will be used for free. + */ + ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL); + if (ptr) { + wq->cpu_wq.single = PTR_ALIGN(ptr, align); + *(void **)(wq->cpu_wq.single + 1) = ptr; + } + } + + /* just in case, make sure it's actually aligned */ + BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align)); + return wq->cpu_wq.v ? 0 : -ENOMEM; +} + +static void free_cwqs(struct workqueue_struct *wq) +{ +#ifdef CONFIG_SMP + bool percpu = !(wq->flags & WQ_UNBOUND); +#else + bool percpu = false; +#endif + + if (percpu) + free_percpu(wq->cpu_wq.pcpu); + else if (wq->cpu_wq.single) { + /* the pointer to free is stored right after the cwq */ + kfree(*(void **)(wq->cpu_wq.single + 1)); + } +} + +static int wq_clamp_max_active(int max_active, unsigned int flags, + const char *name) +{ + int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE; + + if (max_active < 1 || max_active > lim) + printk(KERN_WARNING "workqueue: max_active %d requested for %s " + "is out of range, clamping between %d and %d\n", + max_active, name, 1, lim); + + return clamp_val(max_active, 1, lim); +} + +struct workqueue_struct *__alloc_workqueue_key(const char *name, + unsigned int flags, + int max_active, + struct lock_class_key *key, + const char *lock_name) +{ + struct workqueue_struct *wq; + unsigned int cpu; + + /* + * Workqueues which may be used during memory reclaim should + * have a rescuer to guarantee forward progress. + */ + if (flags & WQ_MEM_RECLAIM) + flags |= WQ_RESCUER; + + /* + * Unbound workqueues aren't concurrency managed and should be + * dispatched to workers immediately. + */ + if (flags & WQ_UNBOUND) + flags |= WQ_HIGHPRI; + + max_active = max_active ?: WQ_DFL_ACTIVE; + max_active = wq_clamp_max_active(max_active, flags, name); + + wq = kzalloc(sizeof(*wq), GFP_KERNEL); + if (!wq) + goto err; + + wq->flags = flags; + wq->saved_max_active = max_active; + mutex_init(&wq->flush_mutex); + atomic_set(&wq->nr_cwqs_to_flush, 0); + INIT_LIST_HEAD(&wq->flusher_queue); + INIT_LIST_HEAD(&wq->flusher_overflow); + + wq->name = name; + lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); + INIT_LIST_HEAD(&wq->list); + + if (alloc_cwqs(wq) < 0) + goto err; + + for_each_cwq_cpu(cpu, wq) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + struct global_cwq *gcwq = get_gcwq(cpu); + + BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK); + cwq->gcwq = gcwq; + cwq->wq = wq; + cwq->flush_color = -1; + cwq->max_active = max_active; + INIT_LIST_HEAD(&cwq->delayed_works); + } + + if (flags & WQ_RESCUER) { + struct worker *rescuer; + + if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL)) + goto err; + + wq->rescuer = rescuer = alloc_worker(); + if (!rescuer) + goto err; + + rescuer->task = kthread_create(rescuer_thread, wq, "%s", name); + if (IS_ERR(rescuer->task)) + goto err; + + rescuer->task->flags |= PF_THREAD_BOUND; + wake_up_process(rescuer->task); + } + + /* + * workqueue_lock protects global freeze state and workqueues + * list. Grab it, set max_active accordingly and add the new + * workqueue to workqueues list. + */ + spin_lock(&workqueue_lock); + + if (workqueue_freezing && wq->flags & WQ_FREEZABLE) + for_each_cwq_cpu(cpu, wq) + get_cwq(cpu, wq)->max_active = 0; + + list_add(&wq->list, &workqueues); + + spin_unlock(&workqueue_lock); + + return wq; +err: + if (wq) { + free_cwqs(wq); + free_mayday_mask(wq->mayday_mask); + kfree(wq->rescuer); + kfree(wq); + } + return NULL; +} +EXPORT_SYMBOL_GPL(__alloc_workqueue_key); + +/** + * destroy_workqueue - safely terminate a workqueue + * @wq: target workqueue + * + * Safely destroy a workqueue. All work currently pending will be done first. + */ +void destroy_workqueue(struct workqueue_struct *wq) +{ + unsigned int flush_cnt = 0; + unsigned int cpu; + + /* + * Mark @wq dying and drain all pending works. Once WQ_DYING is + * set, 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. + */ + wq->flags |= WQ_DYING; +reflush: + flush_workqueue(wq); + + for_each_cwq_cpu(cpu, wq) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + bool drained; + + spin_lock_irq(&cwq->gcwq->lock); + drained = !cwq->nr_active && list_empty(&cwq->delayed_works); + spin_unlock_irq(&cwq->gcwq->lock); + + if (drained) + continue; + + if (++flush_cnt == 10 || + (flush_cnt % 100 == 0 && flush_cnt <= 1000)) + printk(KERN_WARNING "workqueue %s: flush on " + "destruction isn't complete after %u tries\n", + wq->name, flush_cnt); + goto reflush; + } + + /* + * wq list is used to freeze wq, remove from list after + * flushing is complete in case freeze races us. + */ + spin_lock(&workqueue_lock); + list_del(&wq->list); + spin_unlock(&workqueue_lock); + + /* sanity check */ + for_each_cwq_cpu(cpu, wq) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + int i; + + for (i = 0; i < WORK_NR_COLORS; i++) + BUG_ON(cwq->nr_in_flight[i]); + BUG_ON(cwq->nr_active); + BUG_ON(!list_empty(&cwq->delayed_works)); + } + + if (wq->flags & WQ_RESCUER) { + kthread_stop(wq->rescuer->task); + free_mayday_mask(wq->mayday_mask); + kfree(wq->rescuer); + } + + free_cwqs(wq); + kfree(wq); +} +EXPORT_SYMBOL_GPL(destroy_workqueue); + +/** + * workqueue_set_max_active - adjust max_active of a workqueue + * @wq: target workqueue + * @max_active: new max_active value. + * + * Set max_active of @wq to @max_active. + * + * CONTEXT: + * Don't call from IRQ context. + */ +void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) +{ + unsigned int cpu; + + max_active = wq_clamp_max_active(max_active, wq->flags, wq->name); + + spin_lock(&workqueue_lock); + + wq->saved_max_active = max_active; + + for_each_cwq_cpu(cpu, wq) { + struct global_cwq *gcwq = get_gcwq(cpu); + + spin_lock_irq(&gcwq->lock); + + if (!(wq->flags & WQ_FREEZABLE) || + !(gcwq->flags & GCWQ_FREEZING)) + get_cwq(gcwq->cpu, wq)->max_active = max_active; + + spin_unlock_irq(&gcwq->lock); + } + + spin_unlock(&workqueue_lock); +} +EXPORT_SYMBOL_GPL(workqueue_set_max_active); + +/** + * workqueue_congested - test whether a workqueue is congested + * @cpu: CPU in question + * @wq: target workqueue + * + * Test whether @wq's cpu workqueue for @cpu is congested. There is + * no synchronization around this function and the test result is + * unreliable and only useful as advisory hints or for debugging. + * + * RETURNS: + * %true if congested, %false otherwise. + */ +bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq) +{ + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + + return !list_empty(&cwq->delayed_works); +} +EXPORT_SYMBOL_GPL(workqueue_congested); + +/** + * work_cpu - return the last known associated cpu for @work + * @work: the work of interest + * + * RETURNS: + * CPU number if @work was ever queued. WORK_CPU_NONE otherwise. + */ +unsigned int work_cpu(struct work_struct *work) +{ + struct global_cwq *gcwq = get_work_gcwq(work); + + return gcwq ? gcwq->cpu : WORK_CPU_NONE; +} +EXPORT_SYMBOL_GPL(work_cpu); + +/** + * work_busy - test whether a work is currently pending or running + * @work: the work to be tested + * + * Test whether @work is currently pending or running. There is no + * synchronization around this function and the test result is + * unreliable and only useful as advisory hints or for debugging. + * Especially for reentrant wqs, the pending state might hide the + * running state. + * + * RETURNS: + * OR'd bitmask of WORK_BUSY_* bits. + */ +unsigned int work_busy(struct work_struct *work) +{ + struct global_cwq *gcwq = get_work_gcwq(work); + unsigned long flags; + unsigned int ret = 0; + + if (!gcwq) + return false; + + spin_lock_irqsave(&gcwq->lock, flags); + + if (work_pending(work)) + ret |= WORK_BUSY_PENDING; + if (find_worker_executing_work(gcwq, work)) + ret |= WORK_BUSY_RUNNING; + + spin_unlock_irqrestore(&gcwq->lock, flags); + + return ret; +} +EXPORT_SYMBOL_GPL(work_busy); + +/* + * CPU hotplug. + * + * There are two challenges in supporting CPU hotplug. Firstly, there + * are a lot of assumptions on strong associations among work, cwq and + * gcwq which make migrating pending and scheduled works very + * difficult to implement without impacting hot paths. Secondly, + * gcwqs serve mix of short, long and very long running works making + * blocked draining impractical. + * + * This is solved by allowing a gcwq to be detached from CPU, running + * it with unbound (rogue) workers and allowing it to be reattached + * later if the cpu comes back online. A separate thread is created + * to govern a gcwq in such state and is called the trustee of the + * gcwq. + * + * Trustee states and their descriptions. + * + * START Command state used on startup. On CPU_DOWN_PREPARE, a + * new trustee is started with this state. + * + * IN_CHARGE Once started, trustee will enter this state after + * assuming the manager role and making all existing + * workers rogue. DOWN_PREPARE waits for trustee to + * enter this state. After reaching IN_CHARGE, trustee + * tries to execute the pending worklist until it's empty + * and the state is set to BUTCHER, or the state is set + * to RELEASE. + * + * BUTCHER Command state which is set by the cpu callback after + * the cpu has went down. Once this state is set trustee + * knows that there will be no new works on the worklist + * and once the worklist is empty it can proceed to + * killing idle workers. + * + * RELEASE Command state which is set by the cpu callback if the + * cpu down has been canceled or it has come online + * again. After recognizing this state, trustee stops + * trying to drain or butcher and clears ROGUE, rebinds + * all remaining workers back to the cpu and releases + * manager role. + * + * DONE Trustee will enter this state after BUTCHER or RELEASE + * is complete. + * + * trustee CPU draining + * took over down complete + * START -----------> IN_CHARGE -----------> BUTCHER -----------> DONE + * | | ^ + * | CPU is back online v return workers | + * ----------------> RELEASE -------------- + */ + +/** + * trustee_wait_event_timeout - timed event wait for trustee + * @cond: condition to wait for + * @timeout: timeout in jiffies + * + * wait_event_timeout() for trustee to use. Handles locking and + * checks for RELEASE request. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) which may be released and regrabbed + * multiple times. To be used by trustee. + * + * RETURNS: + * Positive indicating left time if @cond is satisfied, 0 if timed + * out, -1 if canceled. + */ +#define trustee_wait_event_timeout(cond, timeout) ({ \ + long __ret = (timeout); \ + while (!((cond) || (gcwq->trustee_state == TRUSTEE_RELEASE)) && \ + __ret) { \ + spin_unlock_irq(&gcwq->lock); \ + __wait_event_timeout(gcwq->trustee_wait, (cond) || \ + (gcwq->trustee_state == TRUSTEE_RELEASE), \ + __ret); \ + spin_lock_irq(&gcwq->lock); \ + } \ + gcwq->trustee_state == TRUSTEE_RELEASE ? -1 : (__ret); \ +}) + +/** + * trustee_wait_event - event wait for trustee + * @cond: condition to wait for + * + * wait_event() for trustee to use. Automatically handles locking and + * checks for CANCEL request. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) which may be released and regrabbed + * multiple times. To be used by trustee. + * + * RETURNS: + * 0 if @cond is satisfied, -1 if canceled. + */ +#define trustee_wait_event(cond) ({ \ + long __ret1; \ + __ret1 = trustee_wait_event_timeout(cond, MAX_SCHEDULE_TIMEOUT);\ + __ret1 < 0 ? -1 : 0; \ +}) + +static int __cpuinit trustee_thread(void *__gcwq) +{ + struct global_cwq *gcwq = __gcwq; + struct worker *worker; + struct work_struct *work; + struct hlist_node *pos; + long rc; + int i; + + BUG_ON(gcwq->cpu != smp_processor_id()); + + spin_lock_irq(&gcwq->lock); + /* + * Claim the manager position and make all workers rogue. + * Trustee must be bound to the target cpu and can't be + * cancelled. + */ + BUG_ON(gcwq->cpu != smp_processor_id()); + rc = trustee_wait_event(!(gcwq->flags & GCWQ_MANAGING_WORKERS)); + BUG_ON(rc < 0); + + gcwq->flags |= GCWQ_MANAGING_WORKERS; + + list_for_each_entry(worker, &gcwq->idle_list, entry) + worker->flags |= WORKER_ROGUE; + + for_each_busy_worker(worker, i, pos, gcwq) + worker->flags |= WORKER_ROGUE; + + /* + * Call schedule() so that we cross rq->lock and thus can + * guarantee sched callbacks see the rogue flag. This is + * necessary as scheduler callbacks may be invoked from other + * cpus. + */ + spin_unlock_irq(&gcwq->lock); + schedule(); + spin_lock_irq(&gcwq->lock); + + /* + * Sched callbacks are disabled now. Zap nr_running. After + * this, nr_running stays zero and need_more_worker() and + * keep_working() are always true as long as the worklist is + * not empty. + */ + atomic_set(get_gcwq_nr_running(gcwq->cpu), 0); + + spin_unlock_irq(&gcwq->lock); + del_timer_sync(&gcwq->idle_timer); + spin_lock_irq(&gcwq->lock); + + /* + * We're now in charge. Notify and proceed to drain. We need + * to keep the gcwq running during the whole CPU down + * procedure as other cpu hotunplug callbacks may need to + * flush currently running tasks. + */ + gcwq->trustee_state = TRUSTEE_IN_CHARGE; + wake_up_all(&gcwq->trustee_wait); + + /* + * The original cpu is in the process of dying and may go away + * anytime now. When that happens, we and all workers would + * be migrated to other cpus. Try draining any left work. We + * want to get it over with ASAP - spam rescuers, wake up as + * many idlers as necessary and create new ones till the + * worklist is empty. Note that if the gcwq is frozen, there + * may be frozen works in freezable cwqs. Don't declare + * completion while frozen. + */ + while (gcwq->nr_workers != gcwq->nr_idle || + gcwq->flags & GCWQ_FREEZING || + gcwq->trustee_state == TRUSTEE_IN_CHARGE) { + int nr_works = 0; + + list_for_each_entry(work, &gcwq->worklist, entry) { + send_mayday(work); + nr_works++; + } + + list_for_each_entry(worker, &gcwq->idle_list, entry) { + if (!nr_works--) + break; + wake_up_process(worker->task); + } + + if (need_to_create_worker(gcwq)) { + spin_unlock_irq(&gcwq->lock); + worker = create_worker(gcwq, false); + spin_lock_irq(&gcwq->lock); + if (worker) { + worker->flags |= WORKER_ROGUE; + start_worker(worker); + } + } + + /* give a breather */ + if (trustee_wait_event_timeout(false, TRUSTEE_COOLDOWN) < 0) + break; + } + + /* + * Either all works have been scheduled and cpu is down, or + * cpu down has already been canceled. Wait for and butcher + * all workers till we're canceled. + */ + do { + rc = trustee_wait_event(!list_empty(&gcwq->idle_list)); + while (!list_empty(&gcwq->idle_list)) + destroy_worker(list_first_entry(&gcwq->idle_list, + struct worker, entry)); + } while (gcwq->nr_workers && rc >= 0); + + /* + * At this point, either draining has completed and no worker + * is left, or cpu down has been canceled or the cpu is being + * brought back up. There shouldn't be any idle one left. + * Tell the remaining busy ones to rebind once it finishes the + * currently scheduled works by scheduling the rebind_work. + */ + WARN_ON(!list_empty(&gcwq->idle_list)); + + for_each_busy_worker(worker, i, pos, gcwq) { + struct work_struct *rebind_work = &worker->rebind_work; + + /* + * Rebind_work may race with future cpu hotplug + * operations. Use a separate flag to mark that + * rebinding is scheduled. + */ + worker->flags |= WORKER_REBIND; + worker->flags &= ~WORKER_ROGUE; + + /* queue rebind_work, wq doesn't matter, use the default one */ + if (test_and_set_bit(WORK_STRUCT_PENDING_BIT, + work_data_bits(rebind_work))) + continue; + + debug_work_activate(rebind_work); + insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work, + worker->scheduled.next, + work_color_to_flags(WORK_NO_COLOR)); + } + + /* relinquish manager role */ + gcwq->flags &= ~GCWQ_MANAGING_WORKERS; + + /* notify completion */ + gcwq->trustee = NULL; + gcwq->trustee_state = TRUSTEE_DONE; + wake_up_all(&gcwq->trustee_wait); + spin_unlock_irq(&gcwq->lock); + return 0; +} + +/** + * wait_trustee_state - wait for trustee to enter the specified state + * @gcwq: gcwq the trustee of interest belongs to + * @state: target state to wait for + * + * Wait for the trustee to reach @state. DONE is already matched. + * + * CONTEXT: + * spin_lock_irq(gcwq->lock) which may be released and regrabbed + * multiple times. To be used by cpu_callback. + */ +static void __cpuinit wait_trustee_state(struct global_cwq *gcwq, int state) +__releases(&gcwq->lock) +__acquires(&gcwq->lock) +{ + if (!(gcwq->trustee_state == state || + gcwq->trustee_state == TRUSTEE_DONE)) { + spin_unlock_irq(&gcwq->lock); + __wait_event(gcwq->trustee_wait, + gcwq->trustee_state == state || + gcwq->trustee_state == TRUSTEE_DONE); + spin_lock_irq(&gcwq->lock); + } +} + +static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, + unsigned long action, + void *hcpu) +{ + unsigned int cpu = (unsigned long)hcpu; + struct global_cwq *gcwq = get_gcwq(cpu); + struct task_struct *new_trustee = NULL; + struct worker *uninitialized_var(new_worker); + unsigned long flags; + + action &= ~CPU_TASKS_FROZEN; + + switch (action) { + case CPU_DOWN_PREPARE: + new_trustee = kthread_create(trustee_thread, gcwq, + "workqueue_trustee/%d\n", cpu); + if (IS_ERR(new_trustee)) + return notifier_from_errno(PTR_ERR(new_trustee)); + kthread_bind(new_trustee, cpu); + /* fall through */ + case CPU_UP_PREPARE: + BUG_ON(gcwq->first_idle); + new_worker = create_worker(gcwq, false); + if (!new_worker) { + if (new_trustee) + kthread_stop(new_trustee); + return NOTIFY_BAD; + } + } + + /* some are called w/ irq disabled, don't disturb irq status */ + spin_lock_irqsave(&gcwq->lock, flags); + + switch (action) { + case CPU_DOWN_PREPARE: + /* initialize trustee and tell it to acquire the gcwq */ + BUG_ON(gcwq->trustee || gcwq->trustee_state != TRUSTEE_DONE); + gcwq->trustee = new_trustee; + gcwq->trustee_state = TRUSTEE_START; + wake_up_process(gcwq->trustee); + wait_trustee_state(gcwq, TRUSTEE_IN_CHARGE); + /* fall through */ + case CPU_UP_PREPARE: + BUG_ON(gcwq->first_idle); + gcwq->first_idle = new_worker; + break; + + case CPU_DYING: + /* + * Before this, the trustee and all workers except for + * the ones which are still executing works from + * before the last CPU down must be on the cpu. After + * this, they'll all be diasporas. + */ + gcwq->flags |= GCWQ_DISASSOCIATED; + break; + + case CPU_POST_DEAD: + gcwq->trustee_state = TRUSTEE_BUTCHER; + /* fall through */ + case CPU_UP_CANCELED: + destroy_worker(gcwq->first_idle); + gcwq->first_idle = NULL; + break; + + case CPU_DOWN_FAILED: + case CPU_ONLINE: + gcwq->flags &= ~GCWQ_DISASSOCIATED; + if (gcwq->trustee_state != TRUSTEE_DONE) { + gcwq->trustee_state = TRUSTEE_RELEASE; + wake_up_process(gcwq->trustee); + wait_trustee_state(gcwq, TRUSTEE_DONE); + } + + /* + * Trustee is done and there might be no worker left. + * Put the first_idle in and request a real manager to + * take a look. + */ + spin_unlock_irq(&gcwq->lock); + kthread_bind(gcwq->first_idle->task, cpu); + spin_lock_irq(&gcwq->lock); + gcwq->flags |= GCWQ_MANAGE_WORKERS; + start_worker(gcwq->first_idle); + gcwq->first_idle = NULL; + break; + } + + spin_unlock_irqrestore(&gcwq->lock, flags); + + return notifier_from_errno(0); +} + +#ifdef CONFIG_SMP + +struct work_for_cpu { + struct completion completion; + long (*fn)(void *); + void *arg; + long ret; +}; + +static int do_work_for_cpu(void *_wfc) +{ + struct work_for_cpu *wfc = _wfc; + wfc->ret = wfc->fn(wfc->arg); + complete(&wfc->completion); + return 0; +} + +/** + * work_on_cpu - run a function in user context on a particular cpu + * @cpu: the cpu to run on + * @fn: the function to run + * @arg: the function arg + * + * This will return the value @fn returns. + * It is up to the caller to ensure that the cpu doesn't go offline. + * The caller must not hold any locks which would prevent @fn from completing. + */ +long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) +{ + struct task_struct *sub_thread; + struct work_for_cpu wfc = { + .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion), + .fn = fn, + .arg = arg, + }; + + sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu"); + if (IS_ERR(sub_thread)) + return PTR_ERR(sub_thread); + kthread_bind(sub_thread, cpu); + wake_up_process(sub_thread); + wait_for_completion(&wfc.completion); + return wfc.ret; +} +EXPORT_SYMBOL_GPL(work_on_cpu); +#endif /* CONFIG_SMP */ + +#ifdef CONFIG_FREEZER + +/** + * freeze_workqueues_begin - begin freezing workqueues + * + * Start freezing workqueues. After this function returns, all freezable + * workqueues will queue new works to their frozen_works list instead of + * gcwq->worklist. + * + * CONTEXT: + * Grabs and releases workqueue_lock and gcwq->lock's. + */ +void freeze_workqueues_begin(void) +{ + unsigned int cpu; + + spin_lock(&workqueue_lock); + + BUG_ON(workqueue_freezing); + workqueue_freezing = true; + + for_each_gcwq_cpu(cpu) { + struct global_cwq *gcwq = get_gcwq(cpu); + struct workqueue_struct *wq; + + spin_lock_irq(&gcwq->lock); + + BUG_ON(gcwq->flags & GCWQ_FREEZING); + gcwq->flags |= GCWQ_FREEZING; + + list_for_each_entry(wq, &workqueues, list) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + + if (cwq && wq->flags & WQ_FREEZABLE) + cwq->max_active = 0; + } + + spin_unlock_irq(&gcwq->lock); + } + + spin_unlock(&workqueue_lock); +} + +/** + * freeze_workqueues_busy - are freezable workqueues still busy? + * + * Check whether freezing is complete. This function must be called + * between freeze_workqueues_begin() and thaw_workqueues(). + * + * CONTEXT: + * Grabs and releases workqueue_lock. + * + * RETURNS: + * %true if some freezable workqueues are still busy. %false if freezing + * is complete. + */ +bool freeze_workqueues_busy(void) +{ + unsigned int cpu; + bool busy = false; + + spin_lock(&workqueue_lock); + + BUG_ON(!workqueue_freezing); + + for_each_gcwq_cpu(cpu) { + struct workqueue_struct *wq; + /* + * nr_active is monotonically decreasing. It's safe + * to peek without lock. + */ + list_for_each_entry(wq, &workqueues, list) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + + if (!cwq || !(wq->flags & WQ_FREEZABLE)) + continue; + + BUG_ON(cwq->nr_active < 0); + if (cwq->nr_active) { + busy = true; + goto out_unlock; + } + } + } +out_unlock: + spin_unlock(&workqueue_lock); + return busy; +} + +/** + * thaw_workqueues - thaw workqueues + * + * Thaw workqueues. Normal queueing is restored and all collected + * frozen works are transferred to their respective gcwq worklists. + * + * CONTEXT: + * Grabs and releases workqueue_lock and gcwq->lock's. + */ +void thaw_workqueues(void) +{ + unsigned int cpu; + + spin_lock(&workqueue_lock); + + if (!workqueue_freezing) + goto out_unlock; + + for_each_gcwq_cpu(cpu) { + struct global_cwq *gcwq = get_gcwq(cpu); + struct workqueue_struct *wq; + + spin_lock_irq(&gcwq->lock); + + BUG_ON(!(gcwq->flags & GCWQ_FREEZING)); + gcwq->flags &= ~GCWQ_FREEZING; + + list_for_each_entry(wq, &workqueues, list) { + struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); + + if (!cwq || !(wq->flags & WQ_FREEZABLE)) + continue; + + /* restore max_active and repopulate worklist */ + cwq->max_active = wq->saved_max_active; + + while (!list_empty(&cwq->delayed_works) && + cwq->nr_active < cwq->max_active) + cwq_activate_first_delayed(cwq); + } + + wake_up_worker(gcwq); + + spin_unlock_irq(&gcwq->lock); + } + + workqueue_freezing = false; +out_unlock: + spin_unlock(&workqueue_lock); +} +#endif /* CONFIG_FREEZER */ + +static int __init init_workqueues(void) +{ + unsigned int cpu; + int i; + + cpu_notifier(workqueue_cpu_callback, CPU_PRI_WORKQUEUE); + + /* initialize gcwqs */ + for_each_gcwq_cpu(cpu) { + struct global_cwq *gcwq = get_gcwq(cpu); + + spin_lock_init(&gcwq->lock); + INIT_LIST_HEAD(&gcwq->worklist); + gcwq->cpu = cpu; + gcwq->flags |= GCWQ_DISASSOCIATED; + + INIT_LIST_HEAD(&gcwq->idle_list); + for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) + INIT_HLIST_HEAD(&gcwq->busy_hash[i]); + + init_timer_deferrable(&gcwq->idle_timer); + gcwq->idle_timer.function = idle_worker_timeout; + gcwq->idle_timer.data = (unsigned long)gcwq; + + setup_timer(&gcwq->mayday_timer, gcwq_mayday_timeout, + (unsigned long)gcwq); + + ida_init(&gcwq->worker_ida); + + gcwq->trustee_state = TRUSTEE_DONE; + init_waitqueue_head(&gcwq->trustee_wait); + } + + /* create the initial worker */ + for_each_online_gcwq_cpu(cpu) { + struct global_cwq *gcwq = get_gcwq(cpu); + struct worker *worker; + + if (cpu != WORK_CPU_UNBOUND) + gcwq->flags &= ~GCWQ_DISASSOCIATED; + worker = create_worker(gcwq, true); + BUG_ON(!worker); + spin_lock_irq(&gcwq->lock); + start_worker(worker); + spin_unlock_irq(&gcwq->lock); + } + + system_wq = alloc_workqueue("events", 0, 0); + system_long_wq = alloc_workqueue("events_long", 0, 0); + system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0); + system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, + WQ_UNBOUND_MAX_ACTIVE); + system_freezable_wq = alloc_workqueue("events_freezable", + WQ_FREEZABLE, 0); + system_nrt_freezable_wq = alloc_workqueue("events_nrt_freezable", + WQ_NON_REENTRANT | WQ_FREEZABLE, 0); + BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq || + !system_unbound_wq || !system_freezable_wq || + !system_nrt_freezable_wq); + return 0; +} +early_initcall(init_workqueues); |