md/dm-vdo/wait-queue.c

15  * vdo_waitq_enqueue_waiter() - Add a waiter to the tail end of a waitq.
16  * @waitq: The vdo_wait_queue to which to add the waiter.
17  * @waiter: The waiter to add to the waitq.
19  * The waiter must not already be waiting in a waitq.
21 void vdo_waitq_enqueue_waiter(struct vdo_wait_queue *waitq, struct vdo_waiter *waiter)
25 	if (waitq->last_waiter == NULL) {
27 		 * The waitq is empty, so form the initial circular list by self-linking the
32 		/* Splice the new waiter in at the end of the waitq. */
33 		waiter->next_waiter = waitq->last_waiter->next_waiter;
34 		waitq->last_waiter->next_waiter = waiter;
38 	waitq->last_waiter = waiter;
39 	waitq->length += 1;
43  * vdo_waitq_transfer_all_waiters() - Transfer all waiters from one waitq to
44  *                                    a second waitq, emptying the first waitq.
45  * @from_waitq: The waitq containing the waiters to move.
46  * @to_waitq: The waitq that will receive the waiters from the first waitq.
51 	/* If the source waitq is empty, there's nothing to do. */
73  * vdo_waitq_notify_all_waiters() - Notify all the entries waiting in a waitq.
74  * @waitq: The vdo_wait_queue containing the waiters to notify.
79  * Notifies all the entries waiting in a waitq to continue execution by invoking a callback
80  * function on each of them in turn. The waitq is copied and emptied before invoking any callbacks,
81  * and only the waiters that were in the waitq at the start of the call will be notified.
83 void vdo_waitq_notify_all_waiters(struct vdo_wait_queue *waitq,
87 	 * Copy and empty the waitq first, avoiding the possibility of an infinite
88 	 * loop if entries are returned to the waitq by the callback function.
93 	vdo_waitq_transfer_all_waiters(waitq, &waiters);
95 	/* Drain the copied waitq, invoking the callback on every entry. */
101  * vdo_waitq_get_first_waiter() - Return the waiter that is at the head end of a waitq.
102  * @waitq: The vdo_wait_queue from which to get the first waiter.
104  * Return: The first (oldest) waiter in the waitq, or NULL if the waitq is empty.
106 struct vdo_waiter *vdo_waitq_get_first_waiter(const struct vdo_wait_queue *waitq)
108 	struct vdo_waiter *last_waiter = waitq->last_waiter;
115 	/* The waitq is circular, so the last entry links to the head of the waitq. */
122  * @waitq: The vdo_wait_queue to process.
127 void vdo_waitq_dequeue_matching_waiters(struct vdo_wait_queue *waitq,
135 	vdo_waitq_transfer_all_waiters(waitq, &iteration_waitq);
141 					  matched_waitq : waitq), waiter);
146  * vdo_waitq_dequeue_waiter() - Remove the first (oldest) waiter from a waitq.
147  * @waitq: The vdo_wait_queue from which to remove the first entry.
152  * Return: The first (oldest) waiter in the waitq, or NULL if the waitq is empty.
154 struct vdo_waiter *vdo_waitq_dequeue_waiter(struct vdo_wait_queue *waitq)
156 	struct vdo_waiter *first_waiter = vdo_waitq_get_first_waiter(waitq);
157 	struct vdo_waiter *last_waiter = waitq->last_waiter;
163 		/* The waitq has a single entry, so empty it by nulling the tail. */
164 		waitq->last_waiter = NULL;
167 		 * The waitq has multiple waiters, so splice the first waiter out
168 		 * of the circular waitq.
173 	/* The waiter is no longer in a waitq. */
175 	waitq->length -= 1;
181  * vdo_waitq_notify_next_waiter() - Notify the next entry waiting in a waitq.
182  * @waitq: The vdo_wait_queue containing the waiter to notify.
187  * Notifies the next entry waiting in a waitq to continue execution by invoking a callback function
188  * on it after removing it from the waitq.
190  * Return: true if there was a waiter in the waitq.
192 bool vdo_waitq_notify_next_waiter(struct vdo_wait_queue *waitq,
195 	struct vdo_waiter *waiter = vdo_waitq_dequeue_waiter(waitq);