[PATCH] Fix task state testing properly in do_signal_stop()

Any tests using < TASK_STOPPED or the like are left over from the time
when the TASK_ZOMBIE and TASK_DEAD bits were in the same word, and it
served to check for "stopped or dead".  I think this one in
do_signal_stop is the only such case.  It has been buggy ever since
exit_state was separated, and isn't testing the exit_state value.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/signal.c

@@ -1763,7 +1763,8 @@ do_signal_stop(int signr)
 				 * stop is always done with the siglock held,
 				 * so this check has no races.
 				 */
-				if (t->state < TASK_STOPPED) {
+				if (!t->exit_state &&
+				    !(t->state & (TASK_STOPPED|TASK_TRACED))) {
 					stop_count++;
 					signal_wake_up(t, 0);
 				}