Function AddWaitEventToSet

src/backend/storage/ipc/latch.c:939–1016

--- * Add an event to the set. Possible events are: * - WL_LATCH_SET: Wait for the latch to be set * - WL_POSTMASTER_DEATH: Wait for postmaster to die * - WL_SOCKET_READABLE: Wait for socket to become readable, * can be combined in one event with other WL_SOCKET_* events * - WL_SOCKET_WRITEABLE: Wait for socket to become writeable, * can be combined with other WL_SOCKET_* events * - WL_S

 * events.
 */
int
AddWaitEventToSet(WaitEventSet *set, uint32 events, pgsocket fd, Latch *latch,
				  void *user_data)
{
	WaitEvent  *event;

	/* not enough space */
	Assert(set->nevents < set->nevents_space);

	if (events == WL_EXIT_ON_PM_DEATH)
	{
		events = WL_POSTMASTER_DEATH;
		set->exit_on_postmaster_death = true;
	}

	if (latch)
	{
		if (latch->owner_pid != MyProcPid)
			elog(ERROR, "cannot wait on a latch owned by another process");
		if (set->latch)
			elog(ERROR, "cannot wait on more than one latch");
		if ((events & WL_LATCH_SET) != WL_LATCH_SET)
			elog(ERROR, "latch events only support being set");
	}
	else
	{
		if (events & WL_LATCH_SET)
			elog(ERROR, "cannot wait on latch without a specified latch");
	}

	/* waiting for socket readiness without a socket indicates a bug */
	if (fd == PGINVALID_SOCKET && (events & WL_SOCKET_MASK))
		elog(ERROR, "cannot wait on socket event without a socket");

	event = &set->events[set->nevents];
	event->pos = set->nevents++;
	event->fd = fd;
	event->events = events;
	event->user_data = user_data;
#ifdef WIN32
	event->reset = false;
#endif

	if (events == WL_LATCH_SET)
	{
		set->latch = latch;
		set->latch_pos = event->pos;
#if defined(WAIT_USE_POLL)
		event->fd = selfpipe_readfd;
#elif defined(WAIT_USE_EPOLL)
		event->fd = signal_fd;
#else
		event->fd = PGINVALID_SOCKET;
#ifdef WAIT_USE_EPOLL
		return event->pos;
#endif
#endif
	}