exit: exit_notify: re-use "dead" list to autoreap current

After the previous change we can add just the exiting EXIT_DEAD task to
the "dead" list and remove another release_task(tsk).

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Sterling Alexander <stalexan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/exit.c

@@ -632,6 +632,8 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
 	}
 
 	tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE;
+	if (tsk->exit_state == EXIT_DEAD)
+		list_add(&tsk->ptrace_entry, &dead);
 
 	/* mt-exec, de_thread() is waiting for group leader */
 	if (unlikely(tsk->signal->notify_count < 0))
@@ -642,10 +644,6 @@ static void exit_notify(struct task_struct *tsk, int group_dead)
 		list_del_init(&p->ptrace_entry);
 		release_task(p);
 	}
-
-	/* If the process is dead, release it - nobody will wait for it */
-	if (autoreap)
-		release_task(tsk);
 }
 
 #ifdef CONFIG_DEBUG_STACK_USAGE