Function StartLMWorker

src/backend/postmaster/postmaster.c:6263–6338

* StartLMWorker * Start a login monitor worker process. * * Like StartAutovacuumWorker, this function is here. As login monitor * worker process is used like normal process, we set backend_type to * NORMAL. */

 * NORMAL.
 */
static void
StartLMWorker(void)
{
	Backend 	*bn;

	/*
	 * If not in condition to run a process, don't try, but handle it like a
	 * fork failure.  This does not normally happen, since the signal is only
	 * supposed to be sent by login monitor launcher when it's OK to do it,
	 * but we have to check to avoid race-condition problems during DB state
	 * changes.
	 */
	if (canAcceptConnections(BACKEND_TYPE_NORMAL) == CAC_OK)
	{
		/*
		 * Compute the cancel key that will be assigned to this session. We
		 * probably don't need cancel keys for autovac workers, but we'd
		 * better have something random in the field to prevent unfriendly
		 * people from sending cancels to them。
		 */
		if (!RandomCancelKey(&MyCancelKey))
		{
			ereport(LOG,
				(errcode(ERRCODE_INTERNAL_ERROR),
					errmsg("could not generate random cancel key")));
			return;
		}

		bn = (Backend *) malloc(sizeof(Backend));
		if (bn)
		{
			bn->cancel_key = MyCancelKey;

			/* Login monitor workers are not dead_end and need a child slot */
			bn->dead_end = false;
			bn->child_slot = MyPMChildSlot = AssignPostmasterChildSlot();
			bn->bgworker_notify = false;

			bn->pid = StartLoginMonitorWorker();
			if (bn->pid > 0)
			{
				bn->bkend_type = BACKEND_TYPE_NORMAL;
				dlist_push_head(&BackendList, &bn->elem);
#ifdef EXEC_BACKEND
				ShmemBackendArrayAdd(bn);
#endif

				/* all OK */
				return;
			}

			/*
			 * fork failed, fall through to report -- actual error message was
			 * logged by StartLoginMonitorWorker
			 */
			(void) ReleasePostmasterChildSlot(bn->child_slot);
			free(bn);
		}