ptrace: do not use task->ptrace directly in core kernel

No functional changes.

- Nobody except ptrace.c & co should use ptrace flags directly, we have
  task_ptrace() for that.

- No need to specially check PT_PTRACED, we must not have other PT_ bits
  set without PT_PTRACED. And no need to know this flag exists.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: 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

@@ -757,7 +757,7 @@ static void reparent_thread(struct task_struct *father, struct task_struct *p,
 	p->exit_signal = SIGCHLD;
 
 	/* If it has exited notify the new parent about this child's death. */
-	if (!p->ptrace &&
+	if (!task_ptrace(p) &&
 	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p)) {
 		do_notify_parent(p, p->exit_signal);
 		if (task_detached(p)) {
@@ -782,7 +782,7 @@ static void forget_original_parent(struct task_struct *father)
 	list_for_each_entry_safe(p, n, &father->children, sibling) {
 		p->real_parent = reaper;
 		if (p->parent == father) {
-			BUG_ON(p->ptrace);
+			BUG_ON(task_ptrace(p));
 			p->parent = p->real_parent;
 		}
 		reparent_thread(father, p, &dead_children);
@@ -1482,7 +1482,7 @@ static int wait_consider_task(struct task_struct *parent, int ptrace,
 		return 0;
 	}
 
-	if (likely(!ptrace) && unlikely(p->ptrace)) {
+	if (likely(!ptrace) && unlikely(task_ptrace(p))) {
 		/*
 		 * This child is hidden by ptrace.
 		 * We aren't allowed to see it now, but eventually we will.