shift "ptrace implies WUNTRACED" from ptrace_do_wait() to wait_task_stopped()

No functional changes, preparation for the next patch.

ptrace_do_wait() adds WUNTRACED to options for wait_task_stopped() which
should always accept the stopped tracee, even if do_wait() was called
without WUNTRACED.

Change wait_task_stopped() to check "ptrace || WUNTRACED" instead.  This
makes the code more explicit, and "int options" argument becomes const in
do_wait() pathes.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/exit.c

@@ -1330,7 +1330,10 @@ static int wait_task_stopped(int ptrace, struct task_struct *p,
 	uid_t uid = 0; /* unneeded, required by compiler */
 	pid_t pid;
 
-	if (!(options & WUNTRACED))
+	/*
+	 * Traditionally we see ptrace'd stopped tasks regardless of options.
+	 */
+	if (!ptrace && !(options & WUNTRACED))
 		return 0;
 
 	exit_code = 0;
@@ -1548,11 +1551,6 @@ static int ptrace_do_wait(struct task_struct *tsk, int *notask_error,
 {
 	struct task_struct *p;
 
-	/*
-	 * Traditionally we see ptrace'd stopped tasks regardless of options.
-	 */
-	options |= WUNTRACED;
-
 	list_for_each_entry(p, &tsk->ptraced, ptrace_entry) {
 		int ret = wait_consider_task(tsk, 1, p, notask_error,
 					     type, pid, options,