runtime: improve startup observability

src/libthecore/socket.cpp

@@ -10,6 +10,31 @@ void socket_timeout(socket_t s, long sec, long usec);
 void socket_reuse(socket_t s);
 void socket_keepalive(socket_t s);
 
+namespace
+{
+bool socket_accept_should_retry()
+{
+#ifdef OS_WINDOWS
+	const int wsa_error = WSAGetLastError();
+	return wsa_error == WSAEWOULDBLOCK || wsa_error == WSAEINTR;
+#else
+#ifdef EINTR
+	if (errno == EINTR)
+		return true;
+#endif
+#ifdef EAGAIN
+	if (errno == EAGAIN)
+		return true;
+#endif
+#ifdef EWOULDBLOCK
+	if (errno == EWOULDBLOCK)
+		return true;
+#endif
+	return false;
+#endif
+}
+}
+
 int socket_read(socket_t desc, char* read_point, size_t space_left)
 {
     int	ret;
@@ -206,6 +231,8 @@ socket_t socket_accept(socket_t s, struct sockaddr_in *peer)
 
     if ((desc = accept(s, (struct sockaddr *) peer, &i)) == -1)
     {
+	if (socket_accept_should_retry())
+		return -1;
 	sys_err("accept: %s (fd %d)", strerror(errno), s);
 	return -1;
     }