From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balbir Singh Subject: Re: Containers: css_put() dilemma Date: Tue, 17 Jul 2007 15:58:33 +0530 Message-ID: <469C99D1.7090807@linux.vnet.ibm.com> References: <469BBE00.8000709@linux.vnet.ibm.com> <6599ad830707161203o7f148c75p52e77d4be3ace487@mail.gmail.com> <469C2792.6050009@linux.vnet.ibm.com> <6599ad830707161935n69776f1t98292fc9990f4766@mail.gmail.com> <20070717070031.GA22410@linux.vnet.ibm.com> <6599ad830707170018p180cb7dfr53e609fd0b186e30@mail.gmail.com> Reply-To: balbir@linux.vnet.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <6599ad830707170018p180cb7dfr53e609fd0b186e30@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: =?windows-1252?Q?=22Paul_=28=3F=3F=29_Menage=22?= Cc: dhaval@linux.vnet.ibm.com, Pavel Emelianov , linux kernel mailing list , Paul Jackson , Linux Containers , Andrew Morton List-Id: containers.vger.kernel.org Paul (??) Menage wrote: > On 7/17/07, Balbir Singh wrote: >> > >> > > mutex_lock(&container_mutex); >> > > set_bit(CONT_RELEASABLE, &cont->flags); >> > >- if (atomic_dec_and_test(&css->refcnt)) { >> > >- check_for_release(cont); >> > >- } >> > >+ check_for_release(cont); >> > > mutex_unlock(&container_mutex); >> > > > > I think that this isn't safe as it stands, without a synchronize_rcu() > in container_diput() prior to the kfree(). Also, it will break if > anyone tries to use a release agent on a hierarchy that has your > memory controller bound to it. > Isn't the code functionally the same as before? We still do atomic_test_and_dec() as before. We still set_bit() CONT_RELEASABLE, we take the container_mutex and check_for_release(). I am not sure I understand what changed? Could you please elaborate as to why using a release agent is broken when the memory controller is attached to it? I am not quite sure why we need the synchronize_rcu() either in container_diput(). > Paul > _______________________________________________ > Containers mailing list > Containers@lists.linux-foundation.org > https://lists.linux-foundation.org/mailman/listinfo/containers -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL