[PATCH] fix non-leader exec under ptrace

This reverts most of commit 30e0fca6c1d7d26f3f2daa4dd2b12c51dadc778a.
It broke the case of non-leader MT exec when ptraced.
I think the bug it was intended to fix was already addressed by commit
788e05a67c343fa22f2ae1d3ca264e7f15c25eaf.

Signed-off-by: Roland McGrath <roland@redhat.com>
Acked-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

kernel/ptrace.c

@@ -56,10 +56,6 @@ void ptrace_untrace(task_t *child)
 			signal_wake_up(child, 1);
 		}
 	}
-	if (child->signal->flags & SIGNAL_GROUP_EXIT) {
-		sigaddset(&child->pending.signal, SIGKILL);
-		signal_wake_up(child, 1);
-	}
 	spin_unlock(&child->sighand->siglock);
 }
 
@@ -81,7 +77,8 @@ void __ptrace_unlink(task_t *child)
 		add_parent(child);
 	}
 
-	ptrace_untrace(child);
+	if (child->state == TASK_TRACED)
+		ptrace_untrace(child);
 }
 
 /*

kernel/signal.c

@@ -1754,9 +1754,9 @@ relock:
 			/* Let the debugger run.  */
 			ptrace_stop(signr, signr, info);
 
-			/* We're back.  Did the debugger cancel the sig or group_exit? */
+			/* We're back.  Did the debugger cancel the sig?  */
 			signr = current->exit_code;
-			if (signr == 0 || current->signal->flags & SIGNAL_GROUP_EXIT)
+			if (signr == 0)
 				continue;
 
 			current->exit_code = 0;