From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753505Ab1LVPf7 (ORCPT ); Thu, 22 Dec 2011 10:35:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51284 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752487Ab1LVPf4 (ORCPT ); Thu, 22 Dec 2011 10:35:56 -0500 Date: Thu, 22 Dec 2011 16:30:04 +0100 From: Oleg Nesterov To: Frederic Weisbecker Cc: Mandeep Singh Baines , Li Zefan , Tejun Heo , LKML , Containers , Cgroups , KAMEZAWA Hiroyuki , Paul Menage , Andrew Morton , "Paul E. McKenney" Subject: Re: Q: cgroup: Questions about possible issues in cgroup locking Message-ID: <20111222153004.GA30522@redhat.com> References: <20111221034334.GD17668@somewhere> <20111221130848.GA19679@redhat.com> <20111221175632.GF17668@somewhere> <20111221190102.GE13529@google.com> <20111221190817.GI17668@somewhere> <20111221192413.GF13529@google.com> <20111221200422.GJ17668@somewhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111221200422.GJ17668@somewhere> 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 On 12/21, Frederic Weisbecker wrote: > > On Wed, Dec 21, 2011 at 11:24:13AM -0800, Mandeep Singh Baines wrote: > > > > If you call exec from a thread other than g, g is now unlinked. So > > "t != g" will always be true. If you then pthread_create, you now > > have two threads so "t != __prev" will also always be true. So > > you now have an infinite loop. > > Oh you're right. > > But then we can't use t != t->group_leader because that assumes while_each_thread() > started on the leader. Yes, this can't work. Besides, we need more burriers to rely on the ->group_leader check. See http://marc.info/?t=127688987300002 in particular, http://marc.info/?l=linux-kernel&m=127714242731448 I think this should work, but then we should do something with the users like zap_threads(). Oleg. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: Q: cgroup: Questions about possible issues in cgroup locking Date: Thu, 22 Dec 2011 16:30:04 +0100 Message-ID: <20111222153004.GA30522@redhat.com> References: <20111221034334.GD17668@somewhere> <20111221130848.GA19679@redhat.com> <20111221175632.GF17668@somewhere> <20111221190102.GE13529@google.com> <20111221190817.GI17668@somewhere> <20111221192413.GF13529@google.com> <20111221200422.GJ17668@somewhere> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20111221200422.GJ17668@somewhere> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Frederic Weisbecker Cc: Mandeep Singh Baines , Li Zefan , Tejun Heo , LKML , Containers , Cgroups , KAMEZAWA Hiroyuki , Paul Menage , Andrew Morton , "Paul E. McKenney" On 12/21, Frederic Weisbecker wrote: > > On Wed, Dec 21, 2011 at 11:24:13AM -0800, Mandeep Singh Baines wrote: > > > > If you call exec from a thread other than g, g is now unlinked. So > > "t != g" will always be true. If you then pthread_create, you now > > have two threads so "t != __prev" will also always be true. So > > you now have an infinite loop. > > Oh you're right. > > But then we can't use t != t->group_leader because that assumes while_each_thread() > started on the leader. Yes, this can't work. Besides, we need more burriers to rely on the ->group_leader check. See http://marc.info/?t=127688987300002 in particular, http://marc.info/?l=linux-kernel&m=127714242731448 I think this should work, but then we should do something with the users like zap_threads(). Oleg.