SLOW_WORK: Add delayed_slow_work support (6b8268b1) · Commits · 方亚芬 / linux

Documentation/slow-work.txt

+15 −1

Original line number	Diff line number	Diff line
		@@ -41,6 +41,13 @@ expand files, provided the time taken to do so isn't too long.
		Operations of both types may sleep during execution, thus tying up the thread
		loaned to it.

		A further class of work item is available, based on the slow work item class:

		(*) Delayed slow work items.

		These are slow work items that have a timer to defer queueing of the item for
		a while.


		THREAD-TO-CLASS ALLOCATION
		--------------------------
		@@ -93,6 +100,10 @@ Slow work items may then be set up by:

		slow_work_init(&myitem, &myitem_ops);

		or:

		delayed_slow_work_init(&myitem, &myitem_ops);

		or:

		vslow_work_init(&myitem, &myitem_ops);
		@@ -104,7 +115,9 @@ A suitably set up work item can then be enqueued for processing:
		int ret = slow_work_enqueue(&myitem);

		This will return a -ve error if the thread pool is unable to gain a reference
		on the item, 0 otherwise.
		on the item, 0 otherwise, or (for delayed work):

		int ret = delayed_slow_work_enqueue(&myitem, my_jiffy_delay);


		The items are reference counted, so there ought to be no need for a flush
		@@ -112,6 +125,7 @@ operation. But as the reference counting is optional, means to cancel
		existing work items are also included:

		cancel_slow_work(&myitem);
		cancel_delayed_slow_work(&myitem);

		can be used to cancel pending work. The above cancel function waits for
		existing work to have been executed (or prevent execution of them, depending

include/linux/slow-work.h

+29 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@
		#ifdef CONFIG_SLOW_WORK

		#include <linux/sysctl.h>
		#include <linux/timer.h>

		struct slow_work;

		@@ -52,10 +53,16 @@ struct slow_work {
		#define SLOW_WORK_ENQ_DEFERRED 2 /* item enqueue deferred */
		#define SLOW_WORK_VERY_SLOW 3 /* item is very slow */
		#define SLOW_WORK_CANCELLING 4 /* item is being cancelled, don't enqueue */
		#define SLOW_WORK_DELAYED 5 /* item is struct delayed_slow_work with active timer */
		const struct slow_work_ops ops; / operations table for this item */
		struct list_head link; /* link in queue */
		};

		struct delayed_slow_work {
		struct slow_work work;
		struct timer_list timer;
		};

		/**
		* slow_work_init - Initialise a slow work item
		* @work: The work item to initialise
		@@ -71,6 +78,20 @@ static inline void slow_work_init(struct slow_work *work,
		INIT_LIST_HEAD(&work->link);
		}

		/**
		* slow_work_init - Initialise a delayed slow work item
		* @work: The work item to initialise
		* @ops: The operations to use to handle the slow work item
		*
		* Initialise a delayed slow work item.
		*/
		static inline void delayed_slow_work_init(struct delayed_slow_work *dwork,
		const struct slow_work_ops *ops)
		{
		init_timer(&dwork->timer);
		slow_work_init(&dwork->work, ops);
		}

		/**
		* vslow_work_init - Initialise a very slow work item
		* @work: The work item to initialise
		@@ -93,6 +114,14 @@ extern void slow_work_cancel(struct slow_work *work);
		extern int slow_work_register_user(struct module *owner);
		extern void slow_work_unregister_user(struct module *owner);

		extern int delayed_slow_work_enqueue(struct delayed_slow_work *dwork,
		unsigned long delay);

		static inline void delayed_slow_work_cancel(struct delayed_slow_work *dwork)
		{
		slow_work_cancel(&dwork->work);
		}

		#ifdef CONFIG_SYSCTL
		extern ctl_table slow_work_sysctls[];
		#endif

kernel/slow-work.c

+127 −2

Original line number	Diff line number	Diff line
		@@ -406,10 +406,39 @@ 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) &&
		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 */
		@@ -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
		*/