kernel/signal.c: change do_signal_stop/do_sigaction to use while_each_thread()

Change do_signal_stop() and do_sigaction() to avoid next_thread() and use
while_each_thread() instead.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -2047,8 +2047,8 @@ static bool do_signal_stop(int signr)
 		if (task_set_jobctl_pending(current, signr | gstop))
 			sig->group_stop_count++;
 
-		for (t = next_thread(current); t != current;
-		     t = next_thread(t)) {
+		t = current;
+		while_each_thread(current, t) {
 			/*
 			 * Setting state to TASK_STOPPED for a group
 			 * stop is always done with the siglock held,
@@ -3125,8 +3125,7 @@ int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 			rm_from_queue_full(&mask, &t->signal->shared_pending);
 			do {
 				rm_from_queue_full(&mask, &t->pending);
-				t = next_thread(t);
-			} while (t != current);
+			} while_each_thread(current, t);
 		}
 	}