X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=kernel%2Fworkqueue.c;h=58e5c152a6bb9c2283937a84ec431eac73fc5b87;hb=1ff8392c32a2645d2665ca779ecb91bb29361c13;hp=fb56fedd5c0274a3458bd0e7cbc8ae4e0d86cf6d;hpb=a9deecba19b8f384d97f82c75379da48bccb2588;p=linux-2.6 diff --git a/kernel/workqueue.c b/kernel/workqueue.c index fb56fedd5c..58e5c152a6 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -47,7 +47,6 @@ struct cpu_workqueue_struct { struct workqueue_struct *wq; struct task_struct *thread; - int should_stop; int run_depth; /* Detect run_workqueue() recursion depth */ } ____cacheline_aligned; @@ -71,7 +70,13 @@ static LIST_HEAD(workqueues); static int singlethread_cpu __read_mostly; static cpumask_t cpu_singlethread_map __read_mostly; -/* optimization, we could use cpu_possible_map */ +/* + * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD + * flushes cwq->worklist. This means that flush_workqueue/wait_on_work + * which comes in between can't use for_each_online_cpu(). We could + * use cpu_possible_map, the cpumask below is more a documentation + * than optimization. + */ static cpumask_t cpu_populated_map __read_mostly; /* If it's single threaded, it isn't in the list of workqueues. */ @@ -272,44 +277,27 @@ static void run_workqueue(struct cpu_workqueue_struct *cwq) spin_unlock_irq(&cwq->lock); } -/* - * NOTE: the caller must not touch *cwq if this func returns true - */ -static int cwq_should_stop(struct cpu_workqueue_struct *cwq) -{ - int should_stop = cwq->should_stop; - - if (unlikely(should_stop)) { - spin_lock_irq(&cwq->lock); - should_stop = cwq->should_stop && list_empty(&cwq->worklist); - if (should_stop) - cwq->thread = NULL; - spin_unlock_irq(&cwq->lock); - } - - return should_stop; -} - static int worker_thread(void *__cwq) { struct cpu_workqueue_struct *cwq = __cwq; DEFINE_WAIT(wait); - if (!cwq->wq->freezeable) - current->flags |= PF_NOFREEZE; + if (cwq->wq->freezeable) + set_freezable(); set_user_nice(current, -5); for (;;) { prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE); - if (!freezing(current) && !cwq->should_stop - && list_empty(&cwq->worklist)) + if (!freezing(current) && + !kthread_should_stop() && + list_empty(&cwq->worklist)) schedule(); finish_wait(&cwq->more_work, &wait); try_to_freeze(); - if (cwq_should_stop(cwq)) + if (kthread_should_stop()) break; run_workqueue(cwq); @@ -340,18 +328,21 @@ static void insert_wq_barrier(struct cpu_workqueue_struct *cwq, insert_work(cwq, &barr->work, tail); } -static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq) +static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq) { + int active; + if (cwq->thread == current) { /* * Probably keventd trying to flush its own queue. So simply run * it by hand rather than deadlocking. */ run_workqueue(cwq); + active = 1; } else { struct wq_barrier barr; - int active = 0; + active = 0; spin_lock_irq(&cwq->lock); if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) { insert_wq_barrier(cwq, &barr, 1); @@ -362,6 +353,8 @@ static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq) if (active) wait_for_completion(&barr.done); } + + return active; } /** @@ -389,16 +382,16 @@ void fastcall flush_workqueue(struct workqueue_struct *wq) EXPORT_SYMBOL_GPL(flush_workqueue); /* - * Upon a successful return, the caller "owns" WORK_STRUCT_PENDING bit, + * 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 cpu_workqueue_struct *cwq; - int ret = 0; + int ret = -1; if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) - return 1; + return 0; /* * The queueing is in progress, or it is already queued. Try to @@ -464,10 +457,28 @@ static void wait_on_work(struct work_struct *work) wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work); } +static int __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)); + + work_clear_pending(work); + return ret; +} + /** * cancel_work_sync - block until a work_struct's callback has terminated * @work: the work which is to be flushed * + * Returns true if @work was pending. + * * cancel_work_sync() will cancel the work if it is queued. If the work's * callback appears to be running, cancel_work_sync() will block until it * has completed. @@ -483,31 +494,26 @@ static void wait_on_work(struct work_struct *work) * The caller must ensure that workqueue_struct on which this work was last * queued can't be destroyed before this function returns. */ -void cancel_work_sync(struct work_struct *work) +int cancel_work_sync(struct work_struct *work) { - while (!try_to_grab_pending(work)) - cpu_relax(); - wait_on_work(work); - work_clear_pending(work); + return __cancel_work_timer(work, NULL); } EXPORT_SYMBOL_GPL(cancel_work_sync); /** - * cancel_rearming_delayed_work - reliably kill off a delayed work. + * cancel_delayed_work_sync - reliably kill off a delayed work. * @dwork: the delayed work struct * + * Returns true if @dwork was pending. + * * It is possible to use this function if @dwork rearms itself via queue_work() * or queue_delayed_work(). See also the comment for cancel_work_sync(). */ -void cancel_rearming_delayed_work(struct delayed_work *dwork) +int cancel_delayed_work_sync(struct delayed_work *dwork) { - while (!del_timer(&dwork->timer) && - !try_to_grab_pending(&dwork->work)) - cpu_relax(); - wait_on_work(&dwork->work); - work_clear_pending(&dwork->work); + return __cancel_work_timer(&dwork->work, &dwork->timer); } -EXPORT_SYMBOL(cancel_rearming_delayed_work); +EXPORT_SYMBOL(cancel_delayed_work_sync); static struct workqueue_struct *keventd_wq __read_mostly; @@ -674,7 +680,6 @@ static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu) return PTR_ERR(p); cwq->thread = p; - cwq->should_stop = 0; return 0; } @@ -740,29 +745,26 @@ EXPORT_SYMBOL_GPL(__create_workqueue); static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu) { - struct wq_barrier barr; - int alive = 0; - - spin_lock_irq(&cwq->lock); - if (cwq->thread != NULL) { - insert_wq_barrier(cwq, &barr, 1); - cwq->should_stop = 1; - alive = 1; - } - spin_unlock_irq(&cwq->lock); - - if (alive) { - wait_for_completion(&barr.done); + /* + * Our caller is either destroy_workqueue() or CPU_DEAD, + * workqueue_mutex protects cwq->thread + */ + if (cwq->thread == NULL) + return; - while (unlikely(cwq->thread != NULL)) - cpu_relax(); - /* - * Wait until cwq->thread unlocks cwq->lock, - * it won't touch *cwq after that. - */ - smp_rmb(); - spin_unlock_wait(&cwq->lock); - } + flush_cpu_workqueue(cwq); + /* + * If the caller is CPU_DEAD and cwq->worklist was not empty, + * a concurrent flush_workqueue() can insert a barrier after us. + * However, in that case run_workqueue() won't return and check + * kthread_should_stop() until it flushes all work_struct's. + * When ->worklist becomes empty it is safe to exit because no + * more work_structs can be queued on this cwq: flush_workqueue + * checks list_empty(), and a "normal" queue_work() can't use + * a dead CPU. + */ + kthread_stop(cwq->thread); + cwq->thread = NULL; } /**