[PATCH] don't let PTRACE_EVENT_EXIT stop hold up SIGKILL

When a thread stops for ptrace exit tracing, it cannot be resumed by
SIGKILL.  Once PF_EXITING is set, SIGKILL will not cause a wakeup from stop
(see wants_signal in kernel/signal.c).  This patch moves the ptrace stop
for exit tracing before the setting of PF_EXITING.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/exit.c

@@ -790,6 +790,12 @@ fastcall NORET_TYPE void do_exit(long code)
 		panic("Attempted to kill init!");
 	if (tsk->io_context)
 		exit_io_context();
+
+	if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
+		current->ptrace_message = code;
+		ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
+	}
+
 	tsk->flags |= PF_EXITING;
 	del_timer_sync(&tsk->real_timer);
 
@@ -798,11 +804,6 @@ fastcall NORET_TYPE void do_exit(long code)
 				current->comm, current->pid,
 				preempt_count());
 
-	if (unlikely(current->ptrace & PT_TRACE_EXIT)) {
-		current->ptrace_message = code;
-		ptrace_notify((PTRACE_EVENT_EXIT << 8) | SIGTRAP);
-	}
-
 	acct_update_integrals();
 	update_mem_hiwater();
 	group_dead = atomic_dec_and_test(&tsk->signal->live);