Please reffer https://www.openembedded.org/pipermail/openembedded-core/2011-July/044923.html
--- a/src/wdm/util.c
+++ b/src/wdm/util.c
@@ -113,8 +113,10 @@ CleanUpChild (void)
 #ifdef CSRG_BASED
 	setsid();
 #else
+	sigset_t sigmask;
 	setpgid (0, getpid ());
-	sigsetmask (0);
+	sigemptyset(&sigmask);
+	sigprocmask(SIG_SETMASK, &sigmask, NULL);
 #endif
 #ifdef SIGCHLD
 	(void) Signal (SIGCHLD, SIG_DFL);