diff options
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/slow-work.c | 94 |
1 files changed, 85 insertions, 9 deletions
diff --git a/kernel/slow-work.c b/kernel/slow-work.c index b763bc2d2670..da94f3c101af 100644 --- a/kernel/slow-work.c +++ b/kernel/slow-work.c @@ -133,6 +133,15 @@ LIST_HEAD(vslow_work_queue); DEFINE_SPINLOCK(slow_work_queue_lock); /* + * The following are two wait queues that get pinged when a work item is placed + * on an empty queue. These allow work items that are hogging a thread by + * sleeping in a way that could be deferred to yield their thread and enqueue + * themselves. + */ +static DECLARE_WAIT_QUEUE_HEAD(slow_work_queue_waits_for_occupation); +static DECLARE_WAIT_QUEUE_HEAD(vslow_work_queue_waits_for_occupation); + +/* * The thread controls. A variable used to signal to the threads that they * should exit when the queue is empty, a waitqueue used by the threads to wait * for signals, and a completion set by the last thread to exit. @@ -306,6 +315,50 @@ auto_requeue: } /** + * slow_work_sleep_till_thread_needed - Sleep till thread needed by other work + * work: The work item under execution that wants to sleep + * _timeout: Scheduler sleep timeout + * + * Allow a requeueable work item to sleep on a slow-work processor thread until + * that thread is needed to do some other work or the sleep is interrupted by + * some other event. + * + * The caller must set up a wake up event before calling this and must have set + * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own + * condition before calling this function as no test is made here. + * + * False is returned if there is nothing on the queue; true is returned if the + * work item should be requeued + */ +bool slow_work_sleep_till_thread_needed(struct slow_work *work, + signed long *_timeout) +{ + wait_queue_head_t *wfo_wq; + struct list_head *queue; + + DEFINE_WAIT(wait); + + if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) { + wfo_wq = &vslow_work_queue_waits_for_occupation; + queue = &vslow_work_queue; + } else { + wfo_wq = &slow_work_queue_waits_for_occupation; + queue = &slow_work_queue; + } + + if (!list_empty(queue)) + return true; + + add_wait_queue_exclusive(wfo_wq, &wait); + if (list_empty(queue)) + *_timeout = schedule_timeout(*_timeout); + finish_wait(wfo_wq, &wait); + + return !list_empty(queue); +} +EXPORT_SYMBOL(slow_work_sleep_till_thread_needed); + +/** * slow_work_enqueue - Schedule a slow work item for processing * @work: The work item to queue * @@ -335,6 +388,8 @@ auto_requeue: */ int slow_work_enqueue(struct slow_work *work) { + wait_queue_head_t *wfo_wq; + struct list_head *queue; unsigned long flags; int ret; @@ -354,6 +409,14 @@ int slow_work_enqueue(struct slow_work *work) * maintaining our promise */ if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) { + if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) { + wfo_wq = &vslow_work_queue_waits_for_occupation; + queue = &vslow_work_queue; + } else { + wfo_wq = &slow_work_queue_waits_for_occupation; + queue = &slow_work_queue; + } + spin_lock_irqsave(&slow_work_queue_lock, flags); if (unlikely(test_bit(SLOW_WORK_CANCELLING, &work->flags))) @@ -380,11 +443,13 @@ int slow_work_enqueue(struct slow_work *work) if (ret < 0) goto failed; slow_work_mark_time(work); - if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) - list_add_tail(&work->link, &vslow_work_queue); - else - list_add_tail(&work->link, &slow_work_queue); + list_add_tail(&work->link, queue); wake_up(&slow_work_thread_wq); + + /* if someone who could be requeued is sleeping on a + * thread, then ask them to yield their thread */ + if (work->link.prev == queue) + wake_up(wfo_wq); } spin_unlock_irqrestore(&slow_work_queue_lock, flags); @@ -487,9 +552,19 @@ EXPORT_SYMBOL(slow_work_cancel); */ static void delayed_slow_work_timer(unsigned long data) { + wait_queue_head_t *wfo_wq; + struct list_head *queue; struct slow_work *work = (struct slow_work *) data; unsigned long flags; - bool queued = false, put = false; + bool queued = false, put = false, first = false; + + if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) { + wfo_wq = &vslow_work_queue_waits_for_occupation; + queue = &vslow_work_queue; + } else { + wfo_wq = &slow_work_queue_waits_for_occupation; + queue = &slow_work_queue; + } spin_lock_irqsave(&slow_work_queue_lock, flags); if (likely(!test_bit(SLOW_WORK_CANCELLING, &work->flags))) { @@ -502,17 +577,18 @@ static void delayed_slow_work_timer(unsigned long data) put = true; } else { slow_work_mark_time(work); - if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) - list_add_tail(&work->link, &vslow_work_queue); - else - list_add_tail(&work->link, &slow_work_queue); + list_add_tail(&work->link, queue); queued = true; + if (work->link.prev == queue) + first = true; } } spin_unlock_irqrestore(&slow_work_queue_lock, flags); if (put) slow_work_put_ref(work); + if (first) + wake_up(wfo_wq); if (queued) wake_up(&slow_work_thread_wq); } |