From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754228Ab1HWPz2 (ORCPT ); Tue, 23 Aug 2011 11:55:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47723 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752435Ab1HWPzV (ORCPT ); Tue, 23 Aug 2011 11:55:21 -0400 Date: Tue, 23 Aug 2011 17:52:21 +0200 From: Oleg Nesterov To: Tejun Heo Cc: rjw@sisk.pl, menage@google.com, linux-kernel@vger.kernel.org, arnd@arndb.de Subject: Re: [PATCH 06/16] freezer: make exiting tasks properly unfreezable Message-ID: <20110823155221.GB25808@redhat.com> References: <1313763382-12341-1-git-send-email-tj@kernel.org> <1313763382-12341-7-git-send-email-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1313763382-12341-7-git-send-email-tj@kernel.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi. Not a comment, but the question. Probably falls into the "read the whole series" category too. On 08/19, Tejun Heo wrote: > > There's no point in freezing an exiting task. This is not clear to me. Probably this is fine, I do not know what the callers of freeze_processes() actually expect. > @@ -915,6 +913,12 @@ 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; OK, but what PF_NOFREEZE actually means? Apart from "dont try to freeze" it means "no need to freeze", yes? IOW, try_to_freeze_tasks() can succeed even if we have a lot of exitinig task which can make some activity, say, disk i/o. Is this correct? Once again, I do not understand the problem-space at all, jus I am curious. Thanks, Oleg.