Function SyncRepQueueInsert

src/backend/replication/syncrep.c:508–536

* Insert MyProc into the specified SyncRepQueue, maintaining sorted invariant. * * Usually we will go at tail of queue, though it's possible that we arrive * here out of order, so start at tail and work back to insertion point. */

 * here out of order, so start at tail and work back to insertion point.
 */
static void
SyncRepQueueInsert(int mode)
{
	PGPROC	   *proc;

	Assert(mode >= 0 && mode < NUM_SYNC_REP_WAIT_MODE);
	proc = (PGPROC *) SHMQueuePrev(&(WalSndCtl->SyncRepQueue[mode]),
								   &(WalSndCtl->SyncRepQueue[mode]),
								   offsetof(PGPROC, syncRepLinks));

	while (proc)
	{
		/*
		 * Stop at the queue element that we should after to ensure the queue
		 * is ordered by LSN.
		 */
		if (proc->waitLSN < MyProc->waitLSN)
			break;

		proc = (PGPROC *) SHMQueuePrev(&(WalSndCtl->SyncRepQueue[mode]),
									   &(proc->syncRepLinks),
									   offsetof(PGPROC, syncRepLinks));
	}

	if (proc)
		SHMQueueInsertAfter(&(proc->syncRepLinks), &(MyProc->syncRepLinks));
	else
		SHMQueueInsertAfter(&(WalSndCtl->SyncRepQueue[mode]), &(MyProc->syncRepLinks));
}

/*
 * Acquire SyncRepLock and cancel any wait currently in progress.