Index: gdb-6.6/gdb/doc/observer.texi
===================================================================
--- gdb-6.6.orig/gdb/doc/observer.texi
+++ gdb-6.6/gdb/doc/observer.texi
@@ -119,6 +119,10 @@ when @value{GDBN} calls this observer, t
 haven't been loaded yet.
 @end deftypefun
 
+@deftypefun void mourn_inferior (struct target_ops *@var{target})
+@value{GDBN} has just detached from an inferior.
+@end deftypefun
+
 @deftypefun void solib_unloaded (struct so_list *@var{solib})
 The shared library specified by @var{solib} has been unloaded.
 @end deftypefun
Index: gdb-6.6/gdb/linux-nat.c
===================================================================
--- gdb-6.6.orig/gdb/linux-nat.c
+++ gdb-6.6/gdb/linux-nat.c
@@ -803,11 +803,23 @@ iterate_over_lwps (int (*callback) (stru
 {
   struct lwp_info *lp, *lpnext;
 
-  for (lp = lwp_list; lp; lp = lpnext)
+  if (lwp_list != NULL)
     {
-      lpnext = lp->next;
+      for (lp = lwp_list; lp; lp = lpnext)
+        {
+          lpnext = lp->next;
+          if ((*callback) (lp, data))
+	    return lp;
+        }
+    }
+  else
+    {
+      /* We are calling iterate_over_lwps for a non-threaded program.
+         Initialize the lwp list to the inferior's ptid.  */
+      lp = add_lwp (BUILD_LWP (GET_PID (inferior_ptid),
+			       GET_PID (inferior_ptid)));
       if ((*callback) (lp, data))
-	return lp;
+        return lp;
     }
 
   return NULL;
@@ -3262,6 +3274,18 @@ linux_nat_add_target (struct target_ops 
   thread_db_init (t);
 }
 
+/* Observer function for a mourn inferior event.  This is needed
+   because if iterate_over_lwps is called for a non-threaded program
+   to handle watchpoints, the lwp list gets initialized but there is
+   no corresponding clean-up when the inferior is detached.  In
+   a threaded program, the observer is simply redundant as the
+   same clean-up gets done in linux_nat_mourn_inferior.  */
+static void
+linux_nat_mourn_inferior_observer (struct target_ops *objfile)
+{
+  init_lwp_list ();
+}
+
 void
 _initialize_linux_nat (void)
 {
@@ -3276,6 +3300,8 @@ Specify any of the following keywords fo
   status   -- list a different bunch of random process info.\n\
   all      -- list all available /proc info."));
 
+  observer_attach_mourn_inferior (linux_nat_mourn_inferior_observer);
+
   /* Save the original signal mask.  */
   sigprocmask (SIG_SETMASK, NULL, &normal_mask);
 
Index: gdb-6.6/gdb/target.c
===================================================================
--- gdb-6.6.orig/gdb/target.c
+++ gdb-6.6/gdb/target.c
@@ -40,6 +40,7 @@
 #include "gdb_assert.h"
 #include "gdbcore.h"
 #include "exceptions.h"
+#include "observer.h"
 
 static void target_info (char *, int);
 
@@ -276,6 +277,13 @@ target_load (char *arg, int from_tty)
   (*current_target.to_load) (arg, from_tty);
 }
 
+void
+target_mourn_inferior (void)
+{
+  (*current_target.to_mourn_inferior) ();
+  observer_notify_mourn_inferior (&current_target);
+}
+
 static int
 nomemory (CORE_ADDR memaddr, char *myaddr, int len, int write,
 	  struct target_ops *t)
Index: gdb-6.6/gdb/target.h
===================================================================
--- gdb-6.6.orig/gdb/target.h
+++ gdb-6.6/gdb/target.h
@@ -891,8 +891,7 @@ int target_follow_fork (int follow_child
 
 /* The inferior process has died.  Do what is right.  */
 
-#define	target_mourn_inferior()	\
-     (*current_target.to_mourn_inferior) ()
+extern void target_mourn_inferior (void);
 
 /* Does target have enough data to do a run or attach command? */