diff options
| -rw-r--r-- | kernel/workqueue.c | 73 |
1 files changed, 53 insertions, 20 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 5c26d36146b..30474c4e107 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -537,9 +537,10 @@ static int work_next_color(int color) * 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. + * set_work_cwq(), set_work_cpu_and_clear_pending() 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 @@ -561,9 +562,10 @@ static void set_work_cwq(struct work_struct *work, WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags); } -static void set_work_cpu(struct work_struct *work, unsigned int cpu) +static void set_work_cpu_and_clear_pending(struct work_struct *work, + unsigned int cpu) { - set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, WORK_STRUCT_PENDING); + set_work_data(work, cpu << WORK_STRUCT_FLAG_BITS, 0); } static void clear_work_data(struct work_struct *work) @@ -981,7 +983,14 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, struct cpu_workqueue_struct *cwq; struct list_head *worklist; unsigned int work_flags; - unsigned long flags; + + /* + * While a work item is PENDING && off queue, a task trying to + * steal the PENDING will busy-loop waiting for it to either get + * queued or lose PENDING. Grabbing PENDING and queueing should + * happen with IRQ disabled. + */ + WARN_ON_ONCE(!irqs_disabled()); debug_work_activate(work); @@ -1008,7 +1017,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) { struct worker *worker; - spin_lock_irqsave(&last_gcwq->lock, flags); + spin_lock(&last_gcwq->lock); worker = find_worker_executing_work(last_gcwq, work); @@ -1016,14 +1025,15 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, gcwq = last_gcwq; else { /* meh... not running there, queue here */ - spin_unlock_irqrestore(&last_gcwq->lock, flags); - spin_lock_irqsave(&gcwq->lock, flags); + spin_unlock(&last_gcwq->lock); + spin_lock(&gcwq->lock); } - } else - spin_lock_irqsave(&gcwq->lock, flags); + } else { + spin_lock(&gcwq->lock); + } } else { gcwq = get_gcwq(WORK_CPU_UNBOUND); - spin_lock_irqsave(&gcwq->lock, flags); + spin_lock(&gcwq->lock); } /* gcwq determined, get cwq and queue */ @@ -1031,7 +1041,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, trace_workqueue_queue_work(cpu, cwq, work); if (WARN_ON(!list_empty(&work->entry))) { - spin_unlock_irqrestore(&gcwq->lock, flags); + spin_unlock(&gcwq->lock); return; } @@ -1049,7 +1059,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, insert_work(cwq, work, worklist, work_flags); - spin_unlock_irqrestore(&gcwq->lock, flags); + spin_unlock(&gcwq->lock); } /** @@ -1067,11 +1077,16 @@ bool queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work) { bool ret = false; + unsigned long flags; + + local_irq_save(flags); if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { __queue_work(cpu, wq, work); ret = true; } + + local_irq_restore(flags); return ret; } EXPORT_SYMBOL_GPL(queue_work_on); @@ -1102,7 +1117,9 @@ 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); + local_irq_disable(); __queue_work(smp_processor_id(), cwq->wq, &dwork->work); + local_irq_enable(); } /** @@ -1120,6 +1137,10 @@ bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, struct timer_list *timer = &dwork->timer; struct work_struct *work = &dwork->work; bool ret = false; + unsigned long flags; + + /* read the comment in __queue_work() */ + local_irq_save(flags); if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { unsigned int lcpu; @@ -1156,6 +1177,8 @@ bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, add_timer(timer); ret = true; } + + local_irq_restore(flags); return ret; } EXPORT_SYMBOL_GPL(queue_delayed_work_on); @@ -1970,15 +1993,13 @@ __acquires(&gcwq->lock) return; } - /* claim and process */ + /* claim and dequeue */ 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); /* @@ -1995,10 +2016,18 @@ __acquires(&gcwq->lock) if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool)) wake_up_worker(pool); - spin_unlock_irq(&gcwq->lock); + /* + * Record the last CPU and clear PENDING. The following wmb is + * paired with the implied mb in test_and_set_bit(PENDING) and + * ensures all updates to @work made here are visible to and + * precede any updates by the next PENDING owner. Also, clear + * PENDING inside @gcwq->lock so that PENDING and queued state + * changes happen together while IRQ is disabled. + */ + smp_wmb(); + set_work_cpu_and_clear_pending(work, gcwq->cpu); - smp_wmb(); /* paired with test_and_set_bit(PENDING) */ - work_clear_pending(work); + spin_unlock_irq(&gcwq->lock); lock_map_acquire_read(&cwq->wq->lockdep_map); lock_map_acquire(&lockdep_map); @@ -2836,9 +2865,11 @@ EXPORT_SYMBOL_GPL(cancel_work_sync); */ bool flush_delayed_work(struct delayed_work *dwork) { + local_irq_disable(); if (del_timer_sync(&dwork->timer)) __queue_work(raw_smp_processor_id(), get_work_cwq(&dwork->work)->wq, &dwork->work); + local_irq_enable(); return flush_work(&dwork->work); } EXPORT_SYMBOL(flush_delayed_work); @@ -2857,9 +2888,11 @@ EXPORT_SYMBOL(flush_delayed_work); */ bool flush_delayed_work_sync(struct delayed_work *dwork) { + local_irq_disable(); if (del_timer_sync(&dwork->timer)) __queue_work(raw_smp_processor_id(), get_work_cwq(&dwork->work)->wq, &dwork->work); + local_irq_enable(); return flush_work_sync(&dwork->work); } EXPORT_SYMBOL(flush_delayed_work_sync); |