ptrace: kill __ptrace_detach(), fix ->exit_state check

Move the code from __ptrace_detach() to its single caller and kill this
helper.

Also, fix the ->exit_state check, we shouldn't wake up EXIT_DEAD tasks.
Actually, I think task_is_stopped_or_traced() makes more sense, but this
needs another patch.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Roland McGrath <roland@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/ptrace.c

@@ -235,16 +235,6 @@ int ptrace_attach(struct task_struct *task)
 	return retval;
 }
 
-static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
-{
-	child->exit_code = data;
-	/* .. re-parent .. */
-	__ptrace_unlink(child);
-	/* .. and wake it up. */
-	if (child->exit_state != EXIT_ZOMBIE)
-		wake_up_process(child);
-}
-
 int ptrace_detach(struct task_struct *child, unsigned int data)
 {
 	if (!valid_signal(data))
@@ -254,10 +244,16 @@ int ptrace_detach(struct task_struct *child, unsigned int data)
 	ptrace_disable(child);
 	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 
-	write_lock_irq(&tasklist_lock);
 	/* protect against de_thread()->release_task() */
-	if (child->ptrace)
-		__ptrace_detach(child, data);
+	write_lock_irq(&tasklist_lock);
+	if (child->ptrace) {
+		child->exit_code = data;
+
+		__ptrace_unlink(child);
+
+		if (!child->exit_state)
+			wake_up_process(child);
+	}
 	write_unlock_irq(&tasklist_lock);
 
 	return 0;