diff options
| -rw-r--r-- | kernel/workqueue.c | 84 |
1 files changed, 44 insertions, 40 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 756761480a1a..248a1e95b577 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -145,7 +145,7 @@ struct worker_pool { struct timer_list idle_timer; /* L: worker idle timeout */ struct timer_list mayday_timer; /* L: SOS timer for workers */ - /* workers are chained either in busy_hash or idle_list */ + /* a workers is either on busy_hash or idle_list, or the manager */ DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER); /* L: hash of busy workers */ @@ -154,8 +154,8 @@ struct worker_pool { struct ida worker_ida; /* L: for worker IDs */ struct workqueue_attrs *attrs; /* I: worker attributes */ - struct hlist_node hash_node; /* R: unbound_pool_hash node */ - int refcnt; /* refcnt for unbound pools */ + struct hlist_node hash_node; /* W: unbound_pool_hash node */ + int refcnt; /* W: refcnt for unbound pools */ /* * The current concurrency level. As it's likely to be accessed @@ -213,8 +213,8 @@ struct wq_flusher { struct wq_device; /* - * The externally visible workqueue abstraction is an array of - * per-CPU workqueues: + * The externally visible workqueue. It relays the issued work items to + * the appropriate worker_pool through its pool_workqueues. */ struct workqueue_struct { unsigned int flags; /* W: WQ_* flags */ @@ -247,9 +247,10 @@ struct workqueue_struct { static struct kmem_cache *pwq_cache; -/* hash of all unbound pools keyed by pool->attrs */ +/* W: hash of all unbound pools keyed by pool->attrs */ static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER); +/* I: attributes used when instantiating standard unbound pools on demand */ static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS]; struct workqueue_struct *system_wq __read_mostly; @@ -434,16 +435,13 @@ static DEFINE_SPINLOCK(workqueue_lock); static LIST_HEAD(workqueues); static bool workqueue_freezing; /* W: have wqs started freezing? */ -/* - * The CPU and unbound standard worker pools. The unbound ones have - * POOL_DISASSOCIATED set, and their workers have WORKER_UNBOUND set. - */ +/* the per-cpu worker pools */ static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS], cpu_worker_pools); /* - * idr of all pools. Modifications are protected by workqueue_lock. Read - * accesses are protected by sched-RCU protected. + * R: idr of all pools. Modifications are protected by workqueue_lock. + * Read accesses are protected by sched-RCU protected. */ static DEFINE_IDR(worker_pool_idr); @@ -890,13 +888,12 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags) * recycled work item as currently executing and make it wait until the * current execution finishes, introducing an unwanted dependency. * - * This function checks the work item address, work function and workqueue - * to avoid false positives. Note that this isn't complete as one may - * construct a work function which can introduce dependency onto itself - * through a recycled work item. Well, if somebody wants to shoot oneself - * in the foot that badly, there's only so much we can do, and if such - * deadlock actually occurs, it should be easy to locate the culprit work - * function. + * This function checks the work item address and work function to avoid + * false positives. Note that this isn't complete as one may construct a + * work function which can introduce dependency onto itself through a + * recycled work item. Well, if somebody wants to shoot oneself in the + * foot that badly, there's only so much we can do, and if such deadlock + * actually occurs, it should be easy to locate the culprit work function. * * CONTEXT: * spin_lock_irq(pool->lock). @@ -1187,9 +1184,9 @@ static void insert_work(struct pool_workqueue *pwq, struct work_struct *work, get_pwq(pwq); /* - * 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. + * Ensure either wq_worker_sleeping() 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(); @@ -1790,6 +1787,10 @@ static struct worker *create_worker(struct worker_pool *pool) if (IS_ERR(worker->task)) goto fail; + /* + * 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_user_nice(worker->task, pool->attrs->nice); set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask); @@ -1950,8 +1951,8 @@ static void pool_mayday_timeout(unsigned long __pool) * sent to all rescuers with works scheduled on @pool to resolve * possible allocation deadlock. * - * On return, need_to_create_worker() is guaranteed to be false and - * may_start_working() true. + * On return, need_to_create_worker() is guaranteed to be %false and + * may_start_working() %true. * * LOCKING: * spin_lock_irq(pool->lock) which may be released and regrabbed @@ -1959,7 +1960,7 @@ static void pool_mayday_timeout(unsigned long __pool) * manager. * * RETURNS: - * false if no action was taken and pool->lock stayed locked, true + * %false if no action was taken and pool->lock stayed locked, %true * otherwise. */ static bool maybe_create_worker(struct worker_pool *pool) @@ -2016,7 +2017,7 @@ restart: * multiple times. Called only from manager. * * RETURNS: - * false if no action was taken and pool->lock stayed locked, true + * %false if no action was taken and pool->lock stayed locked, %true * otherwise. */ static bool maybe_destroy_workers(struct worker_pool *pool) @@ -2268,11 +2269,11 @@ static void process_scheduled_works(struct worker *worker) * worker_thread - the worker thread function * @__worker: self * - * The worker thread function. There are NR_CPU_WORKER_POOLS dynamic pools - * 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(). + * The worker thread function. All workers belong to a worker_pool - + * either a per-cpu one or dynamic unbound one. These workers process all + * work items regardless of their specific target workqueue. The only + * exception is work items which belong to workqueues with a rescuer which + * will be explained in rescuer_thread(). */ static int worker_thread(void *__worker) { @@ -2600,11 +2601,8 @@ static bool flush_workqueue_prep_pwqs(struct workqueue_struct *wq, * 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. + * This function sleeps until all work items which were queued on entry + * have finished execution, but it is not livelocked by new incoming ones. */ void flush_workqueue(struct workqueue_struct *wq) { @@ -2794,7 +2792,7 @@ reflush: if (++flush_cnt == 10 || (flush_cnt % 100 == 0 && flush_cnt <= 1000)) - pr_warn("workqueue %s: flush on destruction isn't complete after %u tries\n", + pr_warn("workqueue %s: drain_workqueue() isn't complete after %u tries\n", wq->name, flush_cnt); local_irq_enable(); @@ -3576,7 +3574,9 @@ static void rcu_free_pool(struct rcu_head *rcu) * @pool: worker_pool to put * * Put @pool. If its refcnt reaches zero, it gets destroyed in sched-RCU - * safe manner. + * safe manner. get_unbound_pool() calls this function on its failure path + * and this function should be able to release pools which went through, + * successfully or not, init_worker_pool(). */ static void put_unbound_pool(struct worker_pool *pool) { @@ -3602,7 +3602,11 @@ static void put_unbound_pool(struct worker_pool *pool) spin_unlock_irq(&workqueue_lock); - /* lock out manager and destroy all workers */ + /* + * Become the manager and destroy all workers. Grabbing + * manager_arb prevents @pool's workers from blocking on + * manager_mutex. + */ mutex_lock(&pool->manager_arb); spin_lock_irq(&pool->lock); @@ -4339,7 +4343,7 @@ EXPORT_SYMBOL_GPL(work_on_cpu); * 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 + * workqueues will queue new works to their delayed_works list instead of * pool->worklist. * * CONTEXT: |