From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753986Ab1HaKVw (ORCPT ); Wed, 31 Aug 2011 06:21:52 -0400 Received: from mail-ew0-f46.google.com ([209.85.215.46]:44431 "EHLO mail-ew0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752107Ab1HaKVv (ORCPT ); Wed, 31 Aug 2011 06:21:51 -0400 Date: Wed, 31 Aug 2011 12:21:43 +0200 From: Tejun Heo To: "Rafael J. Wysocki" , Oleg Nesterov , Paul Menage Cc: containers@lists.linux-foundation.org, linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: [PATCH pm-freezer 2/4] freezer: set PF_NOFREEZE on a dying task right before TASK_DEAD setting bug in freezer_change_state() Message-ID: <20110831102143.GB2828@mtj.dyndns.org> References: <20110831102100.GA2828@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110831102100.GA2828@mtj.dyndns.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3fb45733df "freezer: make exiting tasks properly unfreezable" removed clear_freeze_flag() from exit path and set PF_NOFREEZE right after PTRACE_EVENT_EXIT; however, Oleg pointed out that following exit paths may cause interaction with device drivers after PM freezer consider the system frozen. There's no try_to_freeze() call in the exit path and the only necessary guarantee is that freezer doesn't hang waiting for zombies. Set PF_NOFREEZE right before setting tsk->state to TASK_DEAD instead. Signed-off-by: Tejun Heo Reported-by: Oleg Nesterov Cc: "Rafael J. Wysocki" --- kernel/exit.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) Index: work/kernel/exit.c =================================================================== --- work.orig/kernel/exit.c +++ work/kernel/exit.c @@ -913,12 +913,6 @@ NORET_TYPE void do_exit(long code) ptrace_event(PTRACE_EVENT_EXIT, code); - /* - * With ptrace notification done, there's no point in freezing from - * here on. Disallow freezing. - */ - current->flags |= PF_NOFREEZE; - validate_creds_for_do_exit(tsk); /* @@ -1044,6 +1038,10 @@ NORET_TYPE void do_exit(long code) preempt_disable(); exit_rcu(); + + /* this task is now dead and freezer should ignore it */ + current->flags |= PF_NOFREEZE; + /* causes final put_task_struct in finish_task_switch(). */ tsk->state = TASK_DEAD; schedule();