Function taskq_cancel_id

freebsd/contrib/openzfs/module/os/linux/spl/spl-taskq.c:514–562

* Cancel an already dispatched task given the task id. Still pending tasks * will be immediately canceled, and if the task is active the function will * block until it completes. Preallocated tasks which are canceled must be * freed by the caller. */

 * freed by the caller.
 */
int
taskq_cancel_id(taskq_t *tq, taskqid_t id)
{
	taskq_ent_t *t;
	int rc = ENOENT;
	unsigned long flags;

	ASSERT(tq);

	spin_lock_irqsave_nested(&tq->tq_lock, flags, tq->tq_lock_class);
	t = taskq_find(tq, id);
	if (t && t != ERR_PTR(-EBUSY)) {
		list_del_init(&t->tqent_list);
		t->tqent_flags |= TQENT_FLAG_CANCEL;

		/*
		 * When canceling the lowest outstanding task id we
		 * must recalculate the new lowest outstanding id.
		 */
		if (tq->tq_lowest_id == t->tqent_id) {
			tq->tq_lowest_id = taskq_lowest_id(tq);
			ASSERT3S(tq->tq_lowest_id, >, t->tqent_id);
		}

		/*
		 * The task_expire() function takes the tq->tq_lock so drop
		 * drop the lock before synchronously cancelling the timer.
		 */
		if (timer_pending(&t->tqent_timer)) {
			spin_unlock_irqrestore(&tq->tq_lock, flags);
			del_timer_sync(&t->tqent_timer);
			spin_lock_irqsave_nested(&tq->tq_lock, flags,
			    tq->tq_lock_class);
		}

		if (!(t->tqent_flags & TQENT_FLAG_PREALLOC))
			task_done(tq, t);

		rc = 0;
	}
	spin_unlock_irqrestore(&tq->tq_lock, flags);

	if (t == ERR_PTR(-EBUSY)) {
		taskq_wait_id(tq, id);
		rc = EBUSY;
	}

	return (rc);
}
EXPORT_SYMBOL(taskq_cancel_id);

static int taskq_thread_spawn(taskq_t *tq);