Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933465AbWKWKAU (ORCPT ); Thu, 23 Nov 2006 05:00:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757307AbWKWKAT (ORCPT ); Thu, 23 Nov 2006 05:00:19 -0500 Received: from mailhub.sw.ru ([195.214.233.200]:41663 "EHLO relay.sw.ru") by vger.kernel.org with ESMTP id S1757306AbWKWKAS (ORCPT ); Thu, 23 Nov 2006 05:00:18 -0500 Message-ID: <45657030.7050009@openvz.org> Date: Thu, 23 Nov 2006 12:56:00 +0300 From: Pavel Emelianov User-Agent: Thunderbird 1.5 (X11/20060317) MIME-Version: 1.0 To: Paul Menage CC: Kirill Korotaev , Andrew Morton , ckrm-tech@lists.sourceforge.net, Linux Kernel Mailing List , matthltc@us.ibm.com, hch@infradead.org, Alan Cox , oleg@tv-sign.ru, devel@openvz.org Subject: Re: [ckrm-tech] [PATCH 4/13] BC: context handling References: <45535C18.4040000@sw.ru> <45535E11.20207@sw.ru> <6599ad830611222348o1203357tea64fff91edca4f3@mail.gmail.com> <45655D3E.5020702@openvz.org> <6599ad830611230053m7182698cu897abe5d19471aff@mail.gmail.com> <456567DD.6090703@openvz.org> <6599ad830611230131w1bf63dc1m1998b55b61579509@mail.gmail.com> In-Reply-To: <6599ad830611230131w1bf63dc1m1998b55b61579509@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1592 Lines: 51 Paul Menage wrote: > On 11/23/06, Pavel Emelianov wrote: >> You mean moving is like this: >> >> old_bc = task->real_bc; >> task->real_bc = new_bc; >> cmpxchg(&tsk->exec_bc, old_bc, new_bc); >> >> ? Then this won't work: >> >> Initialisation: >> current->exec_bc = init_bc; >> current->real_bc = init_bc; >> ... >> IRQ: >> current->exec_bc = init_bc; >> ... >> old_bc = tsk->real_bc; /* init_bc */ >> tsk->real_bc = bc1; >> cx(tsk->exec_bc, init_bc, bc1); /* ok */ >> ... >> Here at the middle of an interrupt >> we have bc1 set as exec_bc on task >> which IS wrong! > > You could get round that by having a separate "irq_bc" that's never > valid for a task not in an interrupt. No no no. This is not what is needed. You see, we do have to set exec_bc as temporary (and atomic) context. Having temporary context is 1. flexible 2. needed by beancounters' network accountig. We have to track this particular scenario. Moreover making get_exec_bc() as if (in_interrupt()) return &irq_bc; else return current->exec_bc; is awful. It must me simple and stupid to allow us making temporary contexts in any place of code. Maybe we can make smth similar to wait_task_inactive and change it's beancounter before unlocking the runqueue? > Paul > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/