diff options
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 686 |
1 files changed, 243 insertions, 443 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 193e977a10ea..5dbe22aa3efd 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -65,15 +65,12 @@ enum { * be executing on any CPU. The pool behaves as an unbound one. * * Note that DISASSOCIATED should be flipped only while holding - * manager_mutex to avoid changing binding state while - * create_worker() is in progress. + * attach_mutex to avoid changing binding state while + * worker_attach_to_pool() is in progress. */ - POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */ POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */ - POOL_FREEZING = 1 << 3, /* freeze in progress */ /* worker flags */ - WORKER_STARTED = 1 << 0, /* started */ WORKER_DIE = 1 << 1, /* die die die */ WORKER_IDLE = 1 << 2, /* is idle */ WORKER_PREP = 1 << 3, /* preparing to run works */ @@ -100,10 +97,10 @@ enum { /* * Rescue workers are used only on emergencies and shared by - * all cpus. Give -20. + * all cpus. Give MIN_NICE. */ - RESCUER_NICE_LEVEL = -20, - HIGHPRI_NICE_LEVEL = -20, + RESCUER_NICE_LEVEL = MIN_NICE, + HIGHPRI_NICE_LEVEL = MIN_NICE, WQ_NAME_LEN = 24, }; @@ -124,8 +121,7 @@ enum { * cpu or grabbing pool->lock is enough for read access. If * POOL_DISASSOCIATED is set, it's identical to L. * - * MG: pool->manager_mutex and pool->lock protected. Writes require both - * locks. Reads can happen under either lock. + * A: pool->attach_mutex protected. * * PL: wq_pool_mutex protected. * @@ -163,8 +159,11 @@ struct worker_pool { /* see manage_workers() for details on the two manager mutexes */ struct mutex manager_arb; /* manager arbitration */ - struct mutex manager_mutex; /* manager exclusion */ - struct idr worker_idr; /* MG: worker IDs and iteration */ + struct mutex attach_mutex; /* attach/detach exclusion */ + struct list_head workers; /* A: attached workers */ + struct completion *detach_completion; /* all workers detached */ + + struct ida worker_ida; /* worker IDs for task name */ struct workqueue_attrs *attrs; /* I: worker attributes */ struct hlist_node hash_node; /* PL: unbound_pool_hash node */ @@ -266,7 +265,6 @@ struct workqueue_struct { static struct kmem_cache *pwq_cache; -static int wq_numa_tbl_len; /* highest possible NUMA node id + 1 */ static cpumask_var_t *wq_numa_possible_cpumask; /* possible CPUs of each node */ @@ -340,16 +338,6 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to, lockdep_is_held(&wq->mutex), \ "sched RCU or wq->mutex should be held") -#ifdef CONFIG_LOCKDEP -#define assert_manager_or_pool_lock(pool) \ - WARN_ONCE(debug_locks && \ - !lockdep_is_held(&(pool)->manager_mutex) && \ - !lockdep_is_held(&(pool)->lock), \ - "pool->manager_mutex or ->lock should be held") -#else -#define assert_manager_or_pool_lock(pool) do { } while (0) -#endif - #define for_each_cpu_worker_pool(pool, cpu) \ for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \ (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \ @@ -375,17 +363,16 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to, /** * for_each_pool_worker - iterate through all workers of a worker_pool * @worker: iteration cursor - * @wi: integer used for iteration * @pool: worker_pool to iterate workers of * - * This must be called with either @pool->manager_mutex or ->lock held. + * This must be called with @pool->attach_mutex. * * The if/else clause exists only for the lockdep assertion and can be * ignored. */ -#define for_each_pool_worker(worker, wi, pool) \ - idr_for_each_entry(&(pool)->worker_idr, (worker), (wi)) \ - if (({ assert_manager_or_pool_lock((pool)); false; })) { } \ +#define for_each_pool_worker(worker, pool) \ + list_for_each_entry((worker), &(pool)->workers, node) \ + if (({ lockdep_assert_held(&pool->attach_mutex); false; })) { } \ else /** @@ -516,6 +503,13 @@ void destroy_work_on_stack(struct work_struct *work) } EXPORT_SYMBOL_GPL(destroy_work_on_stack); +void destroy_delayed_work_on_stack(struct delayed_work *work) +{ + destroy_timer_on_stack(&work->timer); + debug_object_free(&work->work, &work_debug_descr); +} +EXPORT_SYMBOL_GPL(destroy_delayed_work_on_stack); + #else static inline void debug_work_activate(struct work_struct *work) { } static inline void debug_work_deactivate(struct work_struct *work) { } @@ -756,13 +750,6 @@ static bool need_to_create_worker(struct worker_pool *pool) return need_more_worker(pool) && !may_start_working(pool); } -/* Do I need to be the manager? */ -static bool need_to_manage_workers(struct worker_pool *pool) -{ - return need_to_create_worker(pool) || - (pool->flags & POOL_MANAGE_WORKERS); -} - /* Do we have too many workers and should some go away? */ static bool too_many_workers(struct worker_pool *pool) { @@ -770,13 +757,6 @@ static bool too_many_workers(struct worker_pool *pool) int nr_idle = pool->nr_idle + managing; /* manager is considered idle */ int nr_busy = pool->nr_workers - nr_idle; - /* - * nr_idle and idle_list may disagree if idle rebinding is in - * progress. Never return %true if idle_list is empty. - */ - if (list_empty(&pool->idle_list)) - return false; - return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy; } @@ -784,8 +764,8 @@ static bool too_many_workers(struct worker_pool *pool) * Wake up functions. */ -/* Return the first worker. Safe with preemption disabled */ -static struct worker *first_worker(struct worker_pool *pool) +/* Return the first idle worker. Safe with preemption disabled */ +static struct worker *first_idle_worker(struct worker_pool *pool) { if (unlikely(list_empty(&pool->idle_list))) return NULL; @@ -804,7 +784,7 @@ static struct worker *first_worker(struct worker_pool *pool) */ static void wake_up_worker(struct worker_pool *pool) { - struct worker *worker = first_worker(pool); + struct worker *worker = first_idle_worker(pool); if (likely(worker)) wake_up_process(worker->task); @@ -862,7 +842,7 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu) pool = worker->pool; /* this can only happen on the local cpu */ - if (WARN_ON_ONCE(cpu != raw_smp_processor_id())) + if (WARN_ON_ONCE(cpu != raw_smp_processor_id() || pool->cpu != cpu)) return NULL; /* @@ -878,7 +858,7 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu) */ if (atomic_dec_and_test(&pool->nr_running) && !list_empty(&pool->worklist)) - to_wakeup = first_worker(pool); + to_wakeup = first_idle_worker(pool); return to_wakeup ? to_wakeup->task : NULL; } @@ -886,35 +866,22 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu) * 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. + * Set @flags in @worker->flags and adjust nr_running accordingly. * * CONTEXT: * spin_lock_irq(pool->lock) */ -static inline void worker_set_flags(struct worker *worker, unsigned int flags, - bool wakeup) +static inline void worker_set_flags(struct worker *worker, unsigned int flags) { struct worker_pool *pool = worker->pool; WARN_ON_ONCE(worker->task != current); - /* - * If transitioning into NOT_RUNNING, adjust nr_running and - * wake up an idle worker as necessary if requested by - * @wakeup. - */ + /* If transitioning into NOT_RUNNING, adjust nr_running. */ if ((flags & WORKER_NOT_RUNNING) && !(worker->flags & WORKER_NOT_RUNNING)) { - if (wakeup) { - if (atomic_dec_and_test(&pool->nr_running) && - !list_empty(&pool->worklist)) - wake_up_worker(pool); - } else - atomic_dec(&pool->nr_running); + atomic_dec(&pool->nr_running); } worker->flags |= flags; @@ -1244,7 +1211,7 @@ static int try_to_grab_pending(struct work_struct *work, bool is_dwork, pwq_activate_delayed_work(work); list_del_init(&work->entry); - pwq_dec_nr_in_flight(get_work_pwq(work), get_work_color(work)); + pwq_dec_nr_in_flight(pwq, get_work_color(work)); /* work->data points to pwq iff queued, point to pool */ set_work_pool_and_keep_pending(work, pool->id); @@ -1572,7 +1539,7 @@ static void worker_enter_idle(struct worker *worker) (worker->hentry.next || worker->hentry.pprev))) return; - /* can't use worker_set_flags(), also called from start_worker() */ + /* can't use worker_set_flags(), also called from create_worker() */ worker->flags |= WORKER_IDLE; pool->nr_idle++; worker->last_active = jiffies; @@ -1614,78 +1581,15 @@ static void worker_leave_idle(struct worker *worker) list_del_init(&worker->entry); } -/** - * worker_maybe_bind_and_lock - try to bind %current to worker_pool and lock it - * @pool: target worker_pool - * - * Bind %current to the cpu of @pool if it is associated and lock @pool. - * - * 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 unbound 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 pool may be - * [dis]associated in the meantime. - * - * This function tries set_cpus_allowed() and locks pool and verifies the - * binding against %POOL_DISASSOCIATED which is set during - * %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker - * enters idle state or fetches works without dropping lock, it can - * guarantee the scheduling requirement described in the first paragraph. - * - * CONTEXT: - * Might sleep. Called without any lock but returns with pool->lock - * held. - * - * Return: - * %true if the associated pool is online (@worker is successfully - * bound), %false if offline. - */ -static bool worker_maybe_bind_and_lock(struct worker_pool *pool) -__acquires(&pool->lock) -{ - while (true) { - /* - * The following call may fail, succeed or succeed - * without actually migrating the task to the cpu if - * it races with cpu hotunplug operation. Verify - * against POOL_DISASSOCIATED. - */ - if (!(pool->flags & POOL_DISASSOCIATED)) - set_cpus_allowed_ptr(current, pool->attrs->cpumask); - - spin_lock_irq(&pool->lock); - if (pool->flags & POOL_DISASSOCIATED) - return false; - if (task_cpu(current) == pool->cpu && - cpumask_equal(¤t->cpus_allowed, pool->attrs->cpumask)) - return true; - spin_unlock_irq(&pool->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(); - } -} - -static struct worker *alloc_worker(void) +static struct worker *alloc_worker(int node) { struct worker *worker; - worker = kzalloc(sizeof(*worker), GFP_KERNEL); + worker = kzalloc_node(sizeof(*worker), GFP_KERNEL, node); if (worker) { INIT_LIST_HEAD(&worker->entry); INIT_LIST_HEAD(&worker->scheduled); + INIT_LIST_HEAD(&worker->node); /* on creation a worker is in !idle && prep state */ worker->flags = WORKER_PREP; } @@ -1693,12 +1597,70 @@ static struct worker *alloc_worker(void) } /** + * worker_attach_to_pool() - attach a worker to a pool + * @worker: worker to be attached + * @pool: the target pool + * + * Attach @worker to @pool. Once attached, the %WORKER_UNBOUND flag and + * cpu-binding of @worker are kept coordinated with the pool across + * cpu-[un]hotplugs. + */ +static void worker_attach_to_pool(struct worker *worker, + struct worker_pool *pool) +{ + mutex_lock(&pool->attach_mutex); + + /* + * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any + * online CPUs. It'll be re-applied when any of the CPUs come up. + */ + set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); + + /* + * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains + * stable across this function. See the comments above the + * flag definition for details. + */ + if (pool->flags & POOL_DISASSOCIATED) + worker->flags |= WORKER_UNBOUND; + + list_add_tail(&worker->node, &pool->workers); + + mutex_unlock(&pool->attach_mutex); +} + +/** + * worker_detach_from_pool() - detach a worker from its pool + * @worker: worker which is attached to its pool + * @pool: the pool @worker is attached to + * + * Undo the attaching which had been done in worker_attach_to_pool(). The + * caller worker shouldn't access to the pool after detached except it has + * other reference to the pool. + */ +static void worker_detach_from_pool(struct worker *worker, + struct worker_pool *pool) +{ + struct completion *detach_completion = NULL; + + mutex_lock(&pool->attach_mutex); + list_del(&worker->node); + if (list_empty(&pool->workers)) + detach_completion = pool->detach_completion; + mutex_unlock(&pool->attach_mutex); + + /* clear leftover flags without pool->lock after it is detached */ + worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND); + + if (detach_completion) + complete(detach_completion); +} + +/** * create_worker - create a new workqueue worker * @pool: pool the new worker will belong to * - * Create a new worker which is bound to @pool. The returned worker - * can be started by calling start_worker() or destroyed using - * destroy_worker(). + * Create and start a new worker which is attached to @pool. * * CONTEXT: * Might sleep. Does GFP_KERNEL allocations. @@ -1712,23 +1674,12 @@ static struct worker *create_worker(struct worker_pool *pool) int id = -1; char id_buf[16]; - lockdep_assert_held(&pool->manager_mutex); - - /* - * ID is needed to determine kthread name. Allocate ID first - * without installing the pointer. - */ - idr_preload(GFP_KERNEL); - spin_lock_irq(&pool->lock); - - id = idr_alloc(&pool->worker_idr, NULL, 0, 0, GFP_NOWAIT); - - spin_unlock_irq(&pool->lock); - idr_preload_end(); + /* ID is needed to determine kthread name */ + id = ida_simple_get(&pool->worker_ida, 0, 0, GFP_KERNEL); if (id < 0) goto fail; - worker = alloc_worker(); + worker = alloc_worker(pool->node); if (!worker) goto fail; @@ -1751,124 +1702,53 @@ static struct worker *create_worker(struct worker_pool *pool) /* prevent userland from meddling with cpumask of workqueue workers */ worker->task->flags |= PF_NO_SETAFFINITY; - /* - * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any - * online CPUs. It'll be re-applied when any of the CPUs come up. - */ - set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); + /* successful, attach the worker to the pool */ + worker_attach_to_pool(worker, pool); - /* - * The caller is responsible for ensuring %POOL_DISASSOCIATED - * remains stable across this function. See the comments above the - * flag definition for details. - */ - if (pool->flags & POOL_DISASSOCIATED) - worker->flags |= WORKER_UNBOUND; - - /* successful, commit the pointer to idr */ + /* start the newly created worker */ spin_lock_irq(&pool->lock); - idr_replace(&pool->worker_idr, worker, worker->id); + worker->pool->nr_workers++; + worker_enter_idle(worker); + wake_up_process(worker->task); spin_unlock_irq(&pool->lock); return worker; fail: - if (id >= 0) { - spin_lock_irq(&pool->lock); - idr_remove(&pool->worker_idr, id); - spin_unlock_irq(&pool->lock); - } + if (id >= 0) + ida_simple_remove(&pool->worker_ida, id); kfree(worker); return NULL; } /** - * start_worker - start a newly created worker - * @worker: worker to start - * - * Make the pool aware of @worker and start it. - * - * CONTEXT: - * spin_lock_irq(pool->lock). - */ -static void start_worker(struct worker *worker) -{ - worker->flags |= WORKER_STARTED; - worker->pool->nr_workers++; - worker_enter_idle(worker); - wake_up_process(worker->task); -} - -/** - * create_and_start_worker - create and start a worker for a pool - * @pool: the target pool - * - * Grab the managership of @pool and create and start a new worker for it. - * - * Return: 0 on success. A negative error code otherwise. - */ -static int create_and_start_worker(struct worker_pool *pool) -{ - struct worker *worker; - - mutex_lock(&pool->manager_mutex); - - worker = create_worker(pool); - if (worker) { - spin_lock_irq(&pool->lock); - start_worker(worker); - spin_unlock_irq(&pool->lock); - } - - mutex_unlock(&pool->manager_mutex); - - return worker ? 0 : -ENOMEM; -} - -/** * destroy_worker - destroy a workqueue worker * @worker: worker to be destroyed * - * Destroy @worker and adjust @pool stats accordingly. + * Destroy @worker and adjust @pool stats accordingly. The worker should + * be idle. * * CONTEXT: - * spin_lock_irq(pool->lock) which is released and regrabbed. + * spin_lock_irq(pool->lock). */ static void destroy_worker(struct worker *worker) { struct worker_pool *pool = worker->pool; - lockdep_assert_held(&pool->manager_mutex); lockdep_assert_held(&pool->lock); /* sanity check frenzy */ if (WARN_ON(worker->current_work) || - WARN_ON(!list_empty(&worker->scheduled))) + WARN_ON(!list_empty(&worker->scheduled)) || + WARN_ON(!(worker->flags & WORKER_IDLE))) return; - if (worker->flags & WORKER_STARTED) - pool->nr_workers--; - if (worker->flags & WORKER_IDLE) - pool->nr_idle--; - - /* - * Once WORKER_DIE is set, the kworker may destroy itself at any - * point. Pin to ensure the task stays until we're done with it. - */ - get_task_struct(worker->task); + pool->nr_workers--; + pool->nr_idle--; list_del_init(&worker->entry); worker->flags |= WORKER_DIE; - - idr_remove(&pool->worker_idr, worker->id); - - spin_unlock_irq(&pool->lock); - - kthread_stop(worker->task); - put_task_struct(worker->task); - kfree(worker); - - spin_lock_irq(&pool->lock); + wake_up_process(worker->task); } static void idle_worker_timeout(unsigned long __pool) @@ -1877,7 +1757,7 @@ static void idle_worker_timeout(unsigned long __pool) spin_lock_irq(&pool->lock); - if (too_many_workers(pool)) { + while (too_many_workers(pool)) { struct worker *worker; unsigned long expires; @@ -1885,13 +1765,12 @@ static void idle_worker_timeout(unsigned long __pool) worker = list_entry(pool->idle_list.prev, struct worker, entry); expires = worker->last_active + IDLE_WORKER_TIMEOUT; - if (time_before(jiffies, expires)) + if (time_before(jiffies, expires)) { mod_timer(&pool->idle_timer, expires); - else { - /* it's been idle for too long, wake up manager */ - pool->flags |= POOL_MANAGE_WORKERS; - wake_up_worker(pool); + break; } + + destroy_worker(worker); } spin_unlock_irq(&pool->lock); @@ -1909,6 +1788,12 @@ static void send_mayday(struct work_struct *work) /* mayday mayday mayday */ if (list_empty(&pwq->mayday_node)) { + /* + * If @pwq is for an unbound wq, its base ref may be put at + * any time due to an attribute change. Pin @pwq until the + * rescuer is done with it. + */ + get_pwq(pwq); list_add_tail(&pwq->mayday_node, &wq->maydays); wake_up_process(wq->rescuer->task); } @@ -1974,23 +1859,10 @@ restart: mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT); while (true) { - struct worker *worker; - - worker = create_worker(pool); - if (worker) { - del_timer_sync(&pool->mayday_timer); - spin_lock_irq(&pool->lock); - start_worker(worker); - if (WARN_ON_ONCE(need_to_create_worker(pool))) - goto restart; - return true; - } - - if (!need_to_create_worker(pool)) + if (create_worker(pool) || !need_to_create_worker(pool)) break; - __set_current_state(TASK_INTERRUPTIBLE); - schedule_timeout(CREATE_COOLDOWN); + schedule_timeout_interruptible(CREATE_COOLDOWN); if (!need_to_create_worker(pool)) break; @@ -1998,50 +1870,17 @@ restart: del_timer_sync(&pool->mayday_timer); spin_lock_irq(&pool->lock); + /* + * This is necessary even after a new worker was just successfully + * created as @pool->lock was dropped and the new worker might have + * already become busy. + */ if (need_to_create_worker(pool)) goto restart; return true; } /** - * maybe_destroy_worker - destroy workers which have been idle for a while - * @pool: pool to destroy workers for - * - * Destroy @pool workers which have been idle for longer than - * IDLE_WORKER_TIMEOUT. - * - * LOCKING: - * spin_lock_irq(pool->lock) which may be released and regrabbed - * multiple times. Called only from manager. - * - * Return: - * %false if no action was taken and pool->lock stayed locked, %true - * otherwise. - */ -static bool maybe_destroy_workers(struct worker_pool *pool) -{ - bool ret = false; - - while (too_many_workers(pool)) { - struct worker *worker; - unsigned long expires; - - worker = list_entry(pool->idle_list.prev, struct worker, entry); - expires = worker->last_active + IDLE_WORKER_TIMEOUT; - - if (time_before(jiffies, expires)) { - mod_timer(&pool->idle_timer, expires); - break; - } - - destroy_worker(worker); - ret = true; - } - - return ret; -} - -/** * manage_workers - manage worker pool * @worker: self * @@ -2070,8 +1909,6 @@ static bool manage_workers(struct worker *worker) bool ret = false; /* - * Managership is governed by two mutexes - manager_arb and - * manager_mutex. manager_arb handles arbitration of manager role. * Anyone who successfully grabs manager_arb wins the arbitration * and becomes the manager. mutex_trylock() on pool->manager_arb * failure while holding pool->lock reliably indicates that someone @@ -2080,40 +1917,12 @@ static bool manage_workers(struct worker *worker) * grabbing manager_arb is responsible for actually performing * manager duties. If manager_arb is grabbed and released without * actual management, the pool may stall indefinitely. - * - * manager_mutex is used for exclusion of actual management - * operations. The holder of manager_mutex can be sure that none - * of management operations, including creation and destruction of - * workers, won't take place until the mutex is released. Because - * manager_mutex doesn't interfere with manager role arbitration, - * it is guaranteed that the pool's management, while may be - * delayed, won't be disturbed by someone else grabbing - * manager_mutex. */ if (!mutex_trylock(&pool->manager_arb)) return ret; - /* - * With manager arbitration won, manager_mutex would be free in - * most cases. trylock first without dropping @pool->lock. - */ - if (unlikely(!mutex_trylock(&pool->manager_mutex))) { - spin_unlock_irq(&pool->lock); - mutex_lock(&pool->manager_mutex); - spin_lock_irq(&pool->lock); - ret = true; - } - - pool->flags &= ~POOL_MANAGE_WORKERS; - - /* - * Destroy and then create so that may_start_working() is true - * on return. - */ - ret |= maybe_destroy_workers(pool); ret |= maybe_create_worker(pool); - mutex_unlock(&pool->manager_mutex); mutex_unlock(&pool->manager_arb); return ret; } @@ -2153,13 +1962,8 @@ __acquires(&pool->lock) lockdep_copy_map(&lockdep_map, &work->lockdep_map); #endif - /* - * Ensure we're on the correct CPU. DISASSOCIATED test is - * necessary to avoid spurious warnings from rescuers servicing the - * unbound or a disassociated pool. - */ - WARN_ON_ONCE(!(worker->flags & WORKER_UNBOUND) && - !(pool->flags & POOL_DISASSOCIATED) && + /* ensure we're on the correct CPU */ + WARN_ON_ONCE(!(pool->flags & POOL_DISASSOCIATED) && raw_smp_processor_id() != pool->cpu); /* @@ -2185,17 +1989,22 @@ __acquires(&pool->lock) list_del_init(&work->entry); /* - * CPU intensive works don't participate in concurrency - * management. They're the scheduler's responsibility. + * CPU intensive works don't participate in concurrency management. + * They're the scheduler's responsibility. This takes @worker out + * of concurrency management and the next code block will chain + * execution of the pending work items. */ if (unlikely(cpu_intensive)) - worker_set_flags(worker, WORKER_CPU_INTENSIVE, true); + worker_set_flags(worker, WORKER_CPU_INTENSIVE); /* - * Unbound pool isn't concurrency managed and work items should be - * executed ASAP. Wake up another worker if necessary. + * Wake up another worker if necessary. The condition is always + * false for normal per-cpu workers since nr_running would always + * be >= 1 at this point. This is used to chain execution of the + * pending work items for WORKER_NOT_RUNNING workers such as the + * UNBOUND and CPU_INTENSIVE ones. */ - if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool)) + if (need_more_worker(pool)) wake_up_worker(pool); /* @@ -2301,6 +2110,11 @@ woke_up: spin_unlock_irq(&pool->lock); WARN_ON_ONCE(!list_empty(&worker->entry)); worker->task->flags &= ~PF_WQ_WORKER; + + set_task_comm(worker->task, "kworker/dying"); + ida_simple_remove(&pool->worker_ida, worker->id); + worker_detach_from_pool(worker, pool); + kfree(worker); return 0; } @@ -2346,11 +2160,8 @@ recheck: } } while (keep_working(pool)); - worker_set_flags(worker, WORKER_PREP, false); + worker_set_flags(worker, WORKER_PREP); sleep: - if (unlikely(need_to_manage_workers(pool)) && manage_workers(worker)) - goto recheck; - /* * pool->lock is held and there's no work to process and no need to * manage, sleep. Workers are woken up only while holding @@ -2391,6 +2202,7 @@ static int rescuer_thread(void *__rescuer) struct worker *rescuer = __rescuer; struct workqueue_struct *wq = rescuer->rescue_wq; struct list_head *scheduled = &rescuer->scheduled; + bool should_stop; set_user_nice(current, RESCUER_NICE_LEVEL); @@ -2402,11 +2214,15 @@ static int rescuer_thread(void *__rescuer) repeat: set_current_state(TASK_INTERRUPTIBLE); - if (kthread_should_stop()) { - __set_current_state(TASK_RUNNING); - rescuer->task->flags &= ~PF_WQ_WORKER; - return 0; - } + /* + * By the time the rescuer is requested to stop, the workqueue + * shouldn't have any work pending, but @wq->maydays may still have + * pwq(s) queued. This can happen by non-rescuer workers consuming + * all the work items before the rescuer got to them. Go through + * @wq->maydays processing before acting on should_stop so that the + * list is always empty on exit. + */ + should_stop = kthread_should_stop(); /* see whether any pwq is asking for help */ spin_lock_irq(&wq_mayday_lock); @@ -2422,8 +2238,9 @@ repeat: spin_unlock_irq(&wq_mayday_lock); - /* migrate to the target cpu if possible */ - worker_maybe_bind_and_lock(pool); + worker_attach_to_pool(rescuer, pool); + + spin_lock_irq(&pool->lock); rescuer->pool = pool; /* @@ -2438,20 +2255,35 @@ repeat: process_scheduled_works(rescuer); /* - * Leave this pool. If keep_working() is %true, notify a + * Put the reference grabbed by send_mayday(). @pool won't + * go away while we're still attached to it. + */ + put_pwq(pwq); + + /* + * Leave this pool. If need_more_worker() is %true, notify a * regular worker; otherwise, we end up with 0 concurrency * and stalling the execution. */ - if (keep_working(pool)) + if (need_more_worker(pool)) wake_up_worker(pool); rescuer->pool = NULL; - spin_unlock(&pool->lock); - spin_lock(&wq_mayday_lock); + spin_unlock_irq(&pool->lock); + + worker_detach_from_pool(rescuer, pool); + + spin_lock_irq(&wq_mayday_lock); } spin_unlock_irq(&wq_mayday_lock); + if (should_stop) { + __set_current_state(TASK_RUNNING); + rescuer->task->flags &= ~PF_WQ_WORKER; + return 0; + } + /* rescuers should never participate in concurrency management */ WARN_ON_ONCE(!(rescuer->flags & WORKER_NOT_RUNNING)); schedule(); @@ -3225,7 +3057,7 @@ static ssize_t wq_nice_store(struct device *dev, struct device_attribute *attr, return -ENOMEM; if (sscanf(buf, "%d", &attrs->nice) == 1 && - attrs->nice >= -20 && attrs->nice <= 19) + attrs->nice >= MIN_NICE && attrs->nice <= MAX_NICE) ret = apply_workqueue_attrs(wq, attrs); else ret = -EINVAL; @@ -3392,6 +3224,7 @@ int workqueue_sysfs_register(struct workqueue_struct *wq) } } + dev_set_uevent_suppress(&wq_dev->dev, false); kobject_uevent(&wq_dev->dev.kobj, KOBJ_ADD); return 0; } @@ -3520,9 +3353,10 @@ static int init_worker_pool(struct worker_pool *pool) (unsigned long)pool); mutex_init(&pool->manager_arb); - mutex_init(&pool->manager_mutex); - idr_init(&pool->worker_idr); + mutex_init(&pool->attach_mutex); + INIT_LIST_HEAD(&pool->workers); + ida_init(&pool->worker_ida); INIT_HLIST_NODE(&pool->hash_node); pool->refcnt = 1; @@ -3537,7 +3371,7 @@ static void rcu_free_pool(struct rcu_head *rcu) { struct worker_pool *pool = container_of(rcu, struct worker_pool, rcu); - idr_destroy(&pool->worker_idr); + ida_destroy(&pool->worker_ida); free_workqueue_attrs(pool->attrs); kfree(pool); } @@ -3555,6 +3389,7 @@ static void rcu_free_pool(struct rcu_head *rcu) */ static void put_unbound_pool(struct worker_pool *pool) { + DECLARE_COMPLETION_ONSTACK(detach_completion); struct worker *worker; lockdep_assert_held(&wq_pool_mutex); @@ -3563,7 +3398,7 @@ static void put_unbound_pool(struct worker_pool *pool) return; /* sanity checks */ - if (WARN_ON(!(pool->flags & POOL_DISASSOCIATED)) || + if (WARN_ON(!(pool->cpu < 0)) || WARN_ON(!list_empty(&pool->worklist))) return; @@ -3575,18 +3410,24 @@ static void put_unbound_pool(struct worker_pool *pool) /* * Become the manager and destroy all workers. Grabbing * manager_arb prevents @pool's workers from blocking on - * manager_mutex. + * attach_mutex. */ mutex_lock(&pool->manager_arb); - mutex_lock(&pool->manager_mutex); - spin_lock_irq(&pool->lock); - while ((worker = first_worker(pool))) + spin_lock_irq(&pool->lock); + while ((worker = first_idle_worker(pool))) destroy_worker(worker); WARN_ON(pool->nr_workers || pool->nr_idle); - spin_unlock_irq(&pool->lock); - mutex_unlock(&pool->manager_mutex); + + mutex_lock(&pool->attach_mutex); + if (!list_empty(&pool->workers)) + pool->detach_completion = &detach_completion; + mutex_unlock(&pool->attach_mutex); + + if (pool->detach_completion) + wait_for_completion(pool->detach_completion); + mutex_unlock(&pool->manager_arb); /* shut down the timers */ @@ -3623,7 +3464,7 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) hash_for_each_possible(unbound_pool_hash, pool, hash_node, hash) { if (wqattrs_equal(pool->attrs, attrs)) { pool->refcnt++; - goto out_unlock; + return pool; } } @@ -3632,9 +3473,6 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) if (!pool || init_worker_pool(pool) < 0) goto fail; - if (workqueue_freezing) - pool->flags |= POOL_FREEZING; - lockdep_set_subclass(&pool->lock, 1); /* see put_pwq() */ copy_workqueue_attrs(pool->attrs, attrs); @@ -3659,12 +3497,12 @@ static struct worker_pool *get_unbound_pool(const struct workqueue_attrs *attrs) goto fail; /* create and start the initial worker */ - if (create_and_start_worker(pool) < 0) + if (!create_worker(pool)) goto fail; /* install */ hash_add(unbound_pool_hash, &pool->hash_node, hash); -out_unlock: + return pool; fail: if (pool) @@ -3693,11 +3531,6 @@ static void pwq_unbound_release_workfn(struct work_struct *work) if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND))) return; - /* - * Unlink @pwq. Synchronization against wq->mutex isn't strictly - * necessary on release but do it anyway. It's easier to verify - * and consistent with the linking path. - */ mutex_lock(&wq->mutex); list_del_rcu(&pwq->pwqs_node); is_last = list_empty(&wq->pwqs); @@ -3741,7 +3574,12 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq) spin_lock_irq(&pwq->pool->lock); - if (!freezable || !(pwq->pool->flags & POOL_FREEZING)) { + /* + * During [un]freezing, the caller is responsible for ensuring that + * this function is called at least once after @workqueue_freezing + * is updated and visible. + */ + if (!freezable || !workqueue_freezing) { pwq->max_active = wq->saved_max_active; while (!list_empty(&pwq->delayed_works) && @@ -3789,10 +3627,7 @@ static void link_pwq(struct pool_workqueue *pwq) if (!list_empty(&pwq->pwqs_node)) return; - /* - * Set the matching work_color. This is synchronized with - * wq->mutex to avoid confusing flush_workqueue(). - */ + /* set the matching work_color */ pwq->work_color = wq->work_color; /* sync max_active to the current setting */ @@ -3929,7 +3764,7 @@ int apply_workqueue_attrs(struct workqueue_struct *wq, if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs))) return -EINVAL; - pwq_tbl = kzalloc(wq_numa_tbl_len * sizeof(pwq_tbl[0]), GFP_KERNEL); + pwq_tbl = kzalloc(nr_node_ids * sizeof(pwq_tbl[0]), GFP_KERNEL); new_attrs = alloc_workqueue_attrs(GFP_KERNEL); tmp_attrs = alloc_workqueue_attrs(GFP_KERNEL); if (!pwq_tbl || !new_attrs || !tmp_attrs) @@ -4073,17 +3908,13 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu, * Let's determine what needs to be done. If the target cpumask is * different from wq's, we need to compare it to @pwq's and create * a new one if they don't match. If the target cpumask equals - * wq's, the default pwq should be used. If @pwq is already the - * default one, nothing to do; otherwise, install the default one. + * wq's, the default pwq should be used. */ if (wq_calc_node_cpumask(wq->unbound_attrs, node, cpu_off, cpumask)) { if (cpumask_equal(cpumask, pwq->pool->attrs->cpumask)) goto out_unlock; } else { - if (pwq == wq->dfl_pwq) - goto out_unlock; - else - goto use_dfl_pwq; + goto use_dfl_pwq; } mutex_unlock(&wq->mutex); @@ -4091,9 +3922,10 @@ static void wq_update_unbound_numa(struct workqueue_struct *wq, int cpu, /* create a new pwq */ pwq = alloc_unbound_pwq(wq, target_attrs); if (!pwq) { - pr_warning("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n", - wq->name); - goto out_unlock; + pr_warn("workqueue: allocation failed while updating NUMA affinity of \"%s\"\n", + wq->name); + mutex_lock(&wq->mutex); + goto use_dfl_pwq; } /* @@ -4180,7 +4012,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, /* allocate wq and format name */ if (flags & WQ_UNBOUND) - tbl_size = wq_numa_tbl_len * sizeof(wq->numa_pwq_tbl[0]); + tbl_size = nr_node_ids * sizeof(wq->numa_pwq_tbl[0]); wq = kzalloc(sizeof(*wq) + tbl_size, GFP_KERNEL); if (!wq) @@ -4222,7 +4054,7 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, if (flags & WQ_MEM_RECLAIM) { struct worker *rescuer; - rescuer = alloc_worker(); + rescuer = alloc_worker(NUMA_NO_NODE); if (!rescuer) goto err_destroy; @@ -4568,28 +4400,25 @@ static void wq_unbind_fn(struct work_struct *work) int cpu = smp_processor_id(); struct worker_pool *pool; struct worker *worker; - int wi; for_each_cpu_worker_pool(pool, cpu) { - WARN_ON_ONCE(cpu != smp_processor_id()); - - mutex_lock(&pool->manager_mutex); + mutex_lock(&pool->attach_mutex); spin_lock_irq(&pool->lock); /* - * We've blocked all manager operations. Make all workers + * We've blocked all attach/detach operations. Make all workers * unbound and set DISASSOCIATED. Before this, all workers * except for the ones which are still executing works from * before the last CPU down must be on the cpu. After * this, they may become diasporas. */ - for_each_pool_worker(worker, wi, pool) + for_each_pool_worker(worker, pool) worker->flags |= WORKER_UNBOUND; pool->flags |= POOL_DISASSOCIATED; spin_unlock_irq(&pool->lock); - mutex_unlock(&pool->manager_mutex); + mutex_unlock(&pool->attach_mutex); /* * Call schedule() so that we cross rq->lock and thus can @@ -4629,9 +4458,8 @@ static void wq_unbind_fn(struct work_struct *work) static void rebind_workers(struct worker_pool *pool) { struct worker *worker; - int wi; - lockdep_assert_held(&pool->manager_mutex); + lockdep_assert_held(&pool->attach_mutex); /* * Restore CPU affinity of all workers. As all idle workers should @@ -4640,13 +4468,14 @@ static void rebind_workers(struct worker_pool *pool) * of all workers first and then clear UNBOUND. As we're called * from CPU_ONLINE, the following shouldn't fail. */ - for_each_pool_worker(worker, wi, pool) + for_each_pool_worker(worker, pool) WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask) < 0); spin_lock_irq(&pool->lock); + pool->flags &= ~POOL_DISASSOCIATED; - for_each_pool_worker(worker, wi, pool) { + for_each_pool_worker(worker, pool) { unsigned int worker_flags = worker->flags; /* @@ -4698,9 +4527,8 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu) { static cpumask_t cpumask; struct worker *worker; - int wi; - lockdep_assert_held(&pool->manager_mutex); + lockdep_assert_held(&pool->attach_mutex); /* is @cpu allowed for @pool? */ if (!cpumask_test_cpu(cpu, pool->attrs->cpumask)) @@ -4712,7 +4540,7 @@ static void restore_unbound_workers_cpumask(struct worker_pool *pool, int cpu) return; /* as we're called from CPU_ONLINE, the following shouldn't fail */ - for_each_pool_worker(worker, wi, pool) + for_each_pool_worker(worker, pool) WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask) < 0); } @@ -4735,7 +4563,7 @@ static int workqueue_cpu_up_callback(struct notifier_block *nfb, for_each_cpu_worker_pool(pool, cpu) { if (pool->nr_workers) continue; - if (create_and_start_worker(pool) < 0) + if (!create_worker(pool)) return NOTIFY_BAD; } break; @@ -4745,19 +4573,14 @@ static int workqueue_cpu_up_callback(struct notifier_block *nfb, mutex_lock(&wq_pool_mutex); for_each_pool(pool, pi) { - mutex_lock(&pool->manager_mutex); - - if (pool->cpu == cpu) { - spin_lock_irq(&pool->lock); - pool->flags &= ~POOL_DISASSOCIATED; - spin_unlock_irq(&pool->lock); + mutex_lock(&pool->attach_mutex); + if (pool->cpu == cpu) rebind_workers(pool); - } else if (pool->cpu < 0) { + else if (pool->cpu < 0) restore_unbound_workers_cpumask(pool, cpu); - } - mutex_unlock(&pool->manager_mutex); + mutex_unlock(&pool->attach_mutex); } /* update NUMA affinity of unbound workqueues */ @@ -4856,24 +4679,14 @@ EXPORT_SYMBOL_GPL(work_on_cpu); */ void freeze_workqueues_begin(void) { - struct worker_pool *pool; struct workqueue_struct *wq; struct pool_workqueue *pwq; - int pi; mutex_lock(&wq_pool_mutex); WARN_ON_ONCE(workqueue_freezing); workqueue_freezing = true; - /* set FREEZING */ - for_each_pool(pool, pi) { - spin_lock_irq(&pool->lock); - WARN_ON_ONCE(pool->flags & POOL_FREEZING); - pool->flags |= POOL_FREEZING; - spin_unlock_irq(&pool->lock); - } - list_for_each_entry(wq, &workqueues, list) { mutex_lock(&wq->mutex); for_each_pwq(pwq, wq) @@ -4943,21 +4756,13 @@ void thaw_workqueues(void) { struct workqueue_struct *wq; struct pool_workqueue *pwq; - struct worker_pool *pool; - int pi; mutex_lock(&wq_pool_mutex); if (!workqueue_freezing) goto out_unlock; - /* clear FREEZING */ - for_each_pool(pool, pi) { - spin_lock_irq(&pool->lock); - WARN_ON_ONCE(!(pool->flags & POOL_FREEZING)); - pool->flags &= ~POOL_FREEZING; - spin_unlock_irq(&pool->lock); - } + workqueue_freezing = false; /* restore max_active and repopulate worklist */ list_for_each_entry(wq, &workqueues, list) { @@ -4967,7 +4772,6 @@ void thaw_workqueues(void) mutex_unlock(&wq->mutex); } - workqueue_freezing = false; out_unlock: mutex_unlock(&wq_pool_mutex); } @@ -4978,10 +4782,6 @@ static void __init wq_numa_init(void) cpumask_var_t *tbl; int node, cpu; - /* determine NUMA pwq table len - highest node id + 1 */ - for_each_node(node) - wq_numa_tbl_len = max(wq_numa_tbl_len, node + 1); - if (num_possible_nodes() <= 1) return; @@ -4998,11 +4798,11 @@ static void __init wq_numa_init(void) * available. Build one from cpu_to_node() which should have been * fully initialized by now. */ - tbl = kzalloc(wq_numa_tbl_len * sizeof(tbl[0]), GFP_KERNEL); + tbl = kzalloc(nr_node_ids * sizeof(tbl[0]), GFP_KERNEL); BUG_ON(!tbl); for_each_node(node) - BUG_ON(!alloc_cpumask_var_node(&tbl[node], GFP_KERNEL, + BUG_ON(!zalloc_cpumask_var_node(&tbl[node], GFP_KERNEL, node_online(node) ? node : NUMA_NO_NODE)); for_each_possible_cpu(cpu) { @@ -5058,7 +4858,7 @@ static int __init init_workqueues(void) for_each_cpu_worker_pool(pool, cpu) { pool->flags &= ~POOL_DISASSOCIATED; - BUG_ON(create_and_start_worker(pool) < 0); + BUG_ON(!create_worker(pool)); } } |
