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SLOW_WORK: Add delayed_slow_work support

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This adds support for starting slow work with a delay, similar
to the functionality we have for workqueues.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
Jens Axboe 2009-11-19 18:10:47 +00:00 • committed by David Howells
parent 0160950297
commit 6b8268b17a
3 changed files with 171 additions and 3 deletions
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129
kernel/slow-work.c
View file

@ -406,11 +406,40 @@ void slow_work_cancel(struct slow_work *work)
bool wait = true, put = false;
set_bit(SLOW_WORK_CANCELLING, &work->flags);
smp_mb();
/* if the work item is a delayed work item with an active timer, we
* need to wait for the timer to finish _before_ getting the spinlock,
* lest we deadlock against the timer routine
*
* the timer routine will leave DELAYED set if it notices the
* CANCELLING flag in time
*/
if (test_bit(SLOW_WORK_DELAYED, &work->flags)) {
struct delayed_slow_work *dwork =
container_of(work, struct delayed_slow_work, work);
del_timer_sync(&dwork->timer);
}
spin_lock_irq(&slow_work_queue_lock);
if (test_bit(SLOW_WORK_PENDING, &work->flags) &&
!list_empty(&work->link)) {
if (test_bit(SLOW_WORK_DELAYED, &work->flags)) {
/* the timer routine aborted or never happened, so we are left
* holding the timer's reference on the item and should just
* drop the pending flag and wait for any ongoing execution to
* finish */
struct delayed_slow_work *dwork =
container_of(work, struct delayed_slow_work, work);
BUG_ON(timer_pending(&dwork->timer));
BUG_ON(!list_empty(&work->link));
clear_bit(SLOW_WORK_DELAYED, &work->flags);
put = true;
clear_bit(SLOW_WORK_PENDING, &work->flags);
} else if (test_bit(SLOW_WORK_PENDING, &work->flags) &&
!list_empty(&work->link)) {
/* the link in the pending queue holds a reference on the item
* that we will need to release */
list_del_init(&work->link);
@ -440,6 +469,102 @@ void slow_work_cancel(struct slow_work *work)
}
EXPORT_SYMBOL(slow_work_cancel);
/*
* Handle expiry of the delay timer, indicating that a delayed slow work item
* should now be queued if not cancelled
*/
static void delayed_slow_work_timer(unsigned long data)
{
struct slow_work *work = (struct slow_work *) data;
unsigned long flags;
bool queued = false, put = false;
spin_lock_irqsave(&slow_work_queue_lock, flags);
if (likely(!test_bit(SLOW_WORK_CANCELLING, &work->flags))) {
clear_bit(SLOW_WORK_DELAYED, &work->flags);
if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) {
/* we discard the reference the timer was holding in
* favour of the one the executor holds */
set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags);
put = true;
} else {
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);
queued = true;
}
}
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
if (put)
slow_work_put_ref(work);
if (queued)
wake_up(&slow_work_thread_wq);
}
/**
* delayed_slow_work_enqueue - Schedule a delayed slow work item for processing
* @dwork: The delayed work item to queue
* @delay: When to start executing the work, in jiffies from now
*
* This is similar to slow_work_enqueue(), but it adds a delay before the work
* is actually queued for processing.
*
* The item can have delayed processing requested on it whilst it is being
* executed. The delay will begin immediately, and if it expires before the
* item finishes executing, the item will be placed back on the queue when it
* has done executing.
*/
int delayed_slow_work_enqueue(struct delayed_slow_work *dwork,
unsigned long delay)
{
struct slow_work *work = &dwork->work;
unsigned long flags;
int ret;
if (delay == 0)
return slow_work_enqueue(&dwork->work);
BUG_ON(slow_work_user_count <= 0);
BUG_ON(!work);
BUG_ON(!work->ops);
if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
return -ECANCELED;
if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) {
spin_lock_irqsave(&slow_work_queue_lock, flags);
if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
goto cancelled;
/* the timer holds a reference whilst it is pending */
ret = work->ops->get_ref(work);
if (ret < 0)
goto cant_get_ref;
if (test_and_set_bit(SLOW_WORK_DELAYED, &work->flags))
BUG();
dwork->timer.expires = jiffies + delay;
dwork->timer.data = (unsigned long) work;
dwork->timer.function = delayed_slow_work_timer;
add_timer(&dwork->timer);
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
}
return 0;
cancelled:
ret = -ECANCELED;
cant_get_ref:
spin_unlock_irqrestore(&slow_work_queue_lock, flags);
return ret;
}
EXPORT_SYMBOL(delayed_slow_work_enqueue);
/*
* Schedule a cull of the thread pool at some time in the near future
*/