util: epoll_run: allow interrupting event polling

If an event handler returns a positive value, the event polling and
handling loop is interrupted after all the pending events indicated by
epoll_wait are processed.

travis-ci: success for lazy-pages: add non-#PF events handling
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/util.c

@@ -1231,6 +1231,7 @@ int epoll_add_rfd(int epfd, struct epoll_rfd *rfd)
 int epoll_run_rfds(int epollfd, struct epoll_event *evs, int nr_fds, int timeout)
 {
 	int ret, i, nr_events;
+	bool have_a_break = false;
 
 	while (1) {
 		/* FIXME -- timeout should decrease over time...  */
@@ -1251,7 +1252,12 @@ int epoll_run_rfds(int epollfd, struct epoll_event *evs, int nr_fds, int timeout
 			ret = rfd->revent(rfd);
 			if (ret < 0)
 				goto out;
+			if (ret > 0)
+				have_a_break = true;
 		}
+
+		if (have_a_break)
+			return 1;
 	}
 out:
 	return ret;