Using read with a timeout does a longjmp() out of a signal handler, which leaves
SIGARLM blocked.  This is inherited by children, and thus not something you
want to do from PID 1.

diff -ru bash/builtins/read.def bash.bak/builtins/read.def
--- bash/builtins/read.def	2002-03-19 13:33:41.000000000 -0600
+++ bash.bak/builtins/read.def	2011-09-07 23:11:56.853885092 -0500
@@ -101,6 +101,11 @@
 sigalrm (s)
      int s;
 {
+  sigset_t walrus;
+
+  sigemptyset(&walrus);
+  sigaddset(&walrus, SIGALRM);
+  sigprocmask(SIG_UNBLOCK, &walrus, 0);
   longjmp (alrmbuf, 1);
 }