Always wait for children inside the event loop

Unfortunatelly, we don't have any way to control asynchronous SIGCHLD
signals which can arrive at the same time, causing ltx to eventually
miss results inside some slots.

For this reason, we need to run waitpid() for all children each time we
receive an event that could be effect of a SIGCHLD.

ltx.c

@@ -184,9 +184,6 @@ static volatile int stop_loop = 0;
 /* it's 1 when stdin/stdout pipes are broken. zero otherwise */
 static volatile int broken_pipe = 0;
 
-/* it's 1 when children completed. zero otherwise */
-static volatile int child_done = 0;
-
 static void ltx_message_reserve_next(struct ltx_session *session)
 {
 	++(session->ltx_message.curr);
@@ -819,7 +816,7 @@ static int ltx_check_stdout(struct ltx_session *session, const int slot_id)
 
 	ssize_t ret = read(slot->event.fd, slot->buffer, READ_BUFFER_SIZE);
 	if (ret == -1) {
-		if (errno != EAGAIN && errno != EWOULDBLOCK)
+		if (errno != EAGAIN && errno != EWOULDBLOCK && errno != EINTR)
 			LTX_HANDLE_ERROR(session, "read() log", 1);
 
 		return 0;
@@ -841,7 +838,7 @@ static int ltx_check_stdout(struct ltx_session *session, const int slot_id)
 	return 1;
 }
 
-static void ltx_send_result(struct ltx_session *session)
+static void ltx_slots_waitpid(struct ltx_session *session)
 {
 	struct ltx_slot *slot;
 	uint64_t slot_id;
@@ -1096,9 +1093,6 @@ static void ltx_signal_handler(int signo)
 	case SIGPIPE:
 		broken_pipe = 1;
 		break;
-	case SIGCHLD:
-		child_done = 1;
-		break;
 	}
 }
 
@@ -1148,7 +1142,6 @@ struct ltx_session *ltx_session_init(const int stdin_fd, const int stdout_fd)
 
 	sigaction(SIGINT, &action, NULL);
 	sigaction(SIGPIPE, &action, NULL);
-	sigaction(SIGCHLD, &action, NULL);
 
 	return session;
 }
@@ -1233,12 +1226,6 @@ static void ltx_event_loop(struct ltx_session *session)
 			goto exit;
 		}
 
-		if (child_done) {
-			ltx_send_result(session);
-			child_done = 0;
-			continue;
-		}
-
 		for (i = 0; i < num; i++) {
 			epoll_evt = events + i;
 			ltx_evt = (struct ltx_event *) epoll_evt->data.ptr;
@@ -1269,6 +1256,8 @@ static void ltx_event_loop(struct ltx_session *session)
 				break;
 			}
 		}
+
+		ltx_slots_waitpid(session);
 	}
 
 exit: