media_server: Fix deadlock when killing from ProcessController

src/servers/media/media_server.cpp

@@ -918,6 +918,13 @@ ServerApp::_ControlThread(void* _server)
 	int32 code;
 	while ((size = read_port_etc(server->_ControlPort(), &code, data,
 			sizeof(data), 0, 0)) > 0) {
+
+		// NOTE: This prevents locks in Deskbar and
+		// possibly in other situations.
+		if (size == B_WOULD_BLOCK) {
+			snooze(100);
+			continue;
+		}
 		server->_HandleMessage(code, data, size);
 	}