Hello, This is something I'm not too sure about, so I rather ask it here: When the context return to userspace on calling poll, is it done in interrupt context ? ... ret = poll(fds, 2, TIMEOUT * 1000); if (ret == -1) { perror ("poll"); return 1; } if (!ret) { return 0; } if (fds[0].revents & POLLIN) printf ("POLLIN\n"); if (fds[1].revents & POLLOUT) printf ("POLLOUT\n"); return 0; Regards, Ran