PFD_SYNCFD
pfd[PFD_SYNCFD].fd = syncfd;
pfd[PFD_SYNCFD].events = POLLIN;
pfd[PFD_SYNCFD].fd = -1;
pfd[PFD_SYNCFD].events = 0;
if (pfd[PFD_SYNCFD].revents & (POLLIN|POLLHUP))