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
--------------------------
slow_work_init(&myitem, &myitem_ops);
+ or:
+
+ delayed_slow_work_init(&myitem, &myitem_ops);
+
or:
vslow_work_init(&myitem, &myitem_ops);
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
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
#ifdef CONFIG_SLOW_WORK
#include <linux/sysctl.h>
+#include <linux/timer.h>
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
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
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
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);
}
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
*/
git://bbs.cooldavid.org / net-next-2.6.git / commitdiff