Move the call to do_signal_stop() down, after tracehook call. This makes

->group_stop_count condition visible to tracers before do_signal_stop()
will participate in this group-stop.

Currently the patch has no effect, tracehook_get_signal() always returns 0.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kernel/signal.c

@@ -1830,11 +1830,6 @@ relock:
 
 	for (;;) {
 		struct k_sigaction *ka;
-
-		if (unlikely(signal->group_stop_count > 0) &&
-		    do_signal_stop(0))
-			goto relock;
-
 		/*
 		 * Tracing can induce an artifical signal and choose sigaction.
 		 * The return value in @signr determines the default action,
@@ -1846,6 +1841,10 @@ relock:
 		if (unlikely(signr != 0))
 			ka = return_ka;
 		else {
+			if (unlikely(signal->group_stop_count > 0) &&
+			    do_signal_stop(0))
+				goto relock;
+
 			signr = dequeue_signal(current, &current->blocked,
 					       info);