Fix some thread_db event model bugs

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Fix some thread_db event model bugs

Kevin Buettner
I found these bugs recently while debugging against an am33 target.  One
is a fairly old bug and was likely not noticed 'til now due to the fact
that a software singlestep target is required to see it.

The other bug is one that I introduced recently when I revised thread-db.c
to not always update the thread list.

        * thread-db.c (handle_thread_db_event): Allow underlying target a
        chance to look at the wait status too.
        (thread_db_check_child_state): Ensure that there's a thread list
        to work with when using the thread_db event model.

Index: thread-db.c
===================================================================
RCS file: /cvs/src/src/rda/unix/thread-db.c,v
retrieving revision 1.16
diff -u -p -r1.16 thread-db.c
--- thread-db.c 8 Nov 2005 21:58:36 -0000 1.16
+++ thread-db.c 2 Dec 2005 00:48:28 -0000
@@ -1853,6 +1853,9 @@ handle_thread_db_event (struct child_pro
       /* We don't have any new status to report...  */
       return 1;
     }
+  /* Give underlying target a chance to look at the wait status.  This
+     is necessary for software singlestep to work correctly.  */
+  handle_waitstatus (process, w);
 
   /* Re-insert the event breakpoints.  */
   insert_thread_db_event_breakpoints (serv);
@@ -2146,11 +2149,19 @@ thread_db_check_child_state (struct chil
      process->stop_signal,
      (unsigned long) debug_get_pc (process->serv, process->pid));
 
-#if ALWAYS_UPDATE_THREAD_LIST
-  /* Update the thread list, and attach to (and thereby stop)
-             any new threads we find.  */
-  update_thread_list (process);
+#if !ALWAYS_UPDATE_THREAD_LIST
+  /* The thread_db event model requires that `event_thread' (see
+     below) gets set correctly, but this won't happen unless there's
+     a thread list to search.  So, if the thread_list is empty and
+     we're using the thread_db event model, we need to update the
+     thread list.  */
+  if (thread_list == NULL && using_thread_db_events)
 #endif
+    {
+      /* Update the thread list, and attach to (and thereby stop)
+ any new threads we find.  */
+      update_thread_list (process);
+    }
 
   process->event_thread = thread_list_lookup_by_lid (process->pid);