diff options
Diffstat (limited to 'kernel/workqueue.c')
| -rw-r--r-- | kernel/workqueue.c | 58 |
1 files changed, 20 insertions, 38 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 52e9abbb7759..0d2514b4ff0d 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -154,15 +154,20 @@ struct worker_pool { unsigned long watchdog_ts; /* L: watchdog timestamp */ - /* The current concurrency level. */ - atomic_t nr_running; + /* + * The counter is incremented in a process context on the associated CPU + * w/ preemption disabled, and decremented or reset in the same context + * but w/ pool->lock held. The readers grab pool->lock and are + * guaranteed to see if the counter reached zero. + */ + int nr_running; struct list_head worklist; /* L: list of pending works */ int nr_workers; /* L: total number of workers */ int nr_idle; /* L: currently idle workers */ - struct list_head idle_list; /* X: list of idle workers */ + struct list_head idle_list; /* L: list of idle workers */ struct timer_list idle_timer; /* L: worker idle timeout */ struct timer_list mayday_timer; /* L: SOS timer for workers */ @@ -777,7 +782,7 @@ static bool work_is_canceling(struct work_struct *work) static bool __need_more_worker(struct worker_pool *pool) { - return !atomic_read(&pool->nr_running); + return !pool->nr_running; } /* @@ -802,8 +807,7 @@ static bool may_start_working(struct worker_pool *pool) /* Do I need to keep working? Called from currently running workers. */ static bool keep_working(struct worker_pool *pool) { - return !list_empty(&pool->worklist) && - atomic_read(&pool->nr_running) <= 1; + return !list_empty(&pool->worklist) && (pool->nr_running <= 1); } /* Do we need a new worker? Called from manager. */ @@ -826,7 +830,7 @@ static bool too_many_workers(struct worker_pool *pool) * Wake up functions. */ -/* Return the first idle worker. Safe with preemption disabled */ +/* Return the first idle worker. Called with pool->lock held. */ static struct worker *first_idle_worker(struct worker_pool *pool) { if (unlikely(list_empty(&pool->idle_list))) @@ -873,7 +877,7 @@ void wq_worker_running(struct task_struct *task) */ preempt_disable(); if (!(worker->flags & WORKER_NOT_RUNNING)) - atomic_inc(&worker->pool->nr_running); + worker->pool->nr_running++; preempt_enable(); worker->sleeping = 0; } @@ -887,7 +891,7 @@ void wq_worker_running(struct task_struct *task) */ void wq_worker_sleeping(struct task_struct *task) { - struct worker *next, *worker = kthread_data(task); + struct worker *worker = kthread_data(task); struct worker_pool *pool; /* @@ -917,23 +921,9 @@ void wq_worker_sleeping(struct task_struct *task) return; } - /* - * The counterpart of the following dec_and_test, implied mb, - * worklist not empty test sequence is in insert_work(). - * Please read comment there. - * - * NOT_RUNNING is clear. This means that we're bound to and - * running on the local cpu w/ rq lock held and preemption - * disabled, which in turn means that none else could be - * manipulating idle_list, so dereferencing idle_list without pool - * lock is safe. - */ - if (atomic_dec_and_test(&pool->nr_running) && - !list_empty(&pool->worklist)) { - next = first_idle_worker(pool); - if (next) - wake_up_process(next->task); - } + pool->nr_running--; + if (need_more_worker(pool)) + wake_up_worker(pool); raw_spin_unlock_irq(&pool->lock); } @@ -987,7 +977,7 @@ static inline void worker_set_flags(struct worker *worker, unsigned int flags) /* If transitioning into NOT_RUNNING, adjust nr_running. */ if ((flags & WORKER_NOT_RUNNING) && !(worker->flags & WORKER_NOT_RUNNING)) { - atomic_dec(&pool->nr_running); + pool->nr_running--; } worker->flags |= flags; @@ -1019,7 +1009,7 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags) */ if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING)) if (!(worker->flags & WORKER_NOT_RUNNING)) - atomic_inc(&pool->nr_running); + pool->nr_running++; } /** @@ -1372,13 +1362,6 @@ static void insert_work(struct pool_workqueue *pwq, struct work_struct *work, list_add_tail(&work->entry, head); get_pwq(pwq); - /* - * 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(); - if (__need_more_worker(pool)) wake_up_worker(pool); } @@ -1827,8 +1810,7 @@ static void worker_enter_idle(struct worker *worker) mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); /* Sanity check nr_running. */ - WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && - atomic_read(&pool->nr_running)); + WARN_ON_ONCE(pool->nr_workers == pool->nr_idle && pool->nr_running); } /** @@ -5006,7 +4988,7 @@ static void unbind_workers(int cpu) * an unbound (in terms of concurrency management) pool which * are served by workers tied to the pool. */ - atomic_set(&pool->nr_running, 0); + pool->nr_running = 0; /* * With concurrency management just turned off, a busy |