From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751870AbXBRTBg (ORCPT ); Sun, 18 Feb 2007 14:01:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751874AbXBRTBg (ORCPT ); Sun, 18 Feb 2007 14:01:36 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:49678 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751870AbXBRTBf (ORCPT ); Sun, 18 Feb 2007 14:01:35 -0500 From: "Rafael J. Wysocki" To: Oleg Nesterov Subject: Re: freezer problems Date: Sun, 18 Feb 2007 19:14:44 +0100 User-Agent: KMail/1.9.5 Cc: ego@in.ibm.com, akpm@osdl.org, paulmck@us.ibm.com, mingo@elte.hu, vatsa@in.ibm.com, dipankar@in.ibm.com, venkatesh.pallipadi@intel.com, linux-kernel@vger.kernel.org, Pavel Machek References: <20070214144031.GA15257@in.ibm.com> <200702181614.38315.rjw@sisk.pl> <20070218161953.GB143@tv-sign.ru> In-Reply-To: <20070218161953.GB143@tv-sign.ru> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200702181914.45757.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sunday, 18 February 2007 17:19, Oleg Nesterov wrote: > On 02/18, Rafael J. Wysocki wrote: > > > > On Sunday, 18 February 2007 15:52, Oleg Nesterov wrote: > > > > > > And now another problem: exec. de_thread() sleeps in TASK_UNINTERRUPTIBLE > > > waiting for all sub-threads to die, and we have the same "deadlock" if > > > one of them is frozen. This is nasty. Probably we can change the ->state > > > to TASK_INTERRUPTIBLE and add try_to_freeze(), or play with the new PF_ > > > flag, but I am not sure it is safe to freeze() the task which is deep > > > in the exec() path. > > > > Hm, I haven't been aware of this case. > > > > Well, probably we can do something like in the patch that I've just sent: the > > child that enters the refrigerator should know that the parent is > > uninterruptible and will wait for it to exit. Thus it can either mark the > > parent as frozen or just exit the refrigerator without freezing itself. > > Sub-thread could already sleep in refrigerator when another thread does exec. > So we have no choice but somehow freeze the execer. But again, I don't know > if it is safe to freeze it here, at de_thread() stage. It is called from > load_xxx_binary(), we may hold some important locks... So it probably isn't safe. Rafael