Function SHMQueueInsertBefore

src/backend/storage/ipc/shmqueue.c:88–100

* SHMQueueInsertBefore -- put elem in queue before the given queue * element. Inserting "before" the queue head puts the elem * at the tail of the queue. */

 *		at the tail of the queue.
 */
void
SHMQueueInsertBefore(SHM_QUEUE *queue, SHM_QUEUE *elem)
{
	SHM_QUEUE  *prevPtr = queue->prev;

	Assert(ShmemAddrIsValid(queue));
	Assert(ShmemAddrIsValid(elem));

	elem->next = prevPtr->next;
	elem->prev = queue->prev;
	queue->prev = elem;
	prevPtr->next = elem;
}

/*
 * SHMQueueInsertAfter -- put elem in queue after the given queue