Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757921AbXFZOxV (ORCPT ); Tue, 26 Jun 2007 10:53:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754352AbXFZOxO (ORCPT ); Tue, 26 Jun 2007 10:53:14 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:46842 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752085AbXFZOxN (ORCPT ); Tue, 26 Jun 2007 10:53:13 -0400 Date: Tue, 26 Jun 2007 07:53:09 -0700 From: "Paul E. McKenney" To: Oleg Nesterov Cc: "Rafael J. Wysocki" , Andrew Morton , Nigel Cunningham , Pavel Machek , Uli Luckas , linux-kernel@vger.kernel.org Subject: Re: synchronize_qrcu_timeout() Message-ID: <20070626145308.GA8929@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20070625104332.GA147@tv-sign.ru> <20070625145851.GB12976@linux.vnet.ibm.com> <20070625152011.GA160@tv-sign.ru> <20070625154957.GA197@tv-sign.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070625154957.GA197@tv-sign.ru> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2414 Lines: 77 On Mon, Jun 25, 2007 at 07:49:57PM +0400, Oleg Nesterov wrote: > On 06/25, Oleg Nesterov wrote: > > > > On 06/25, Paul E. McKenney wrote: > > > > > > On Mon, Jun 25, 2007 at 02:43:32PM +0400, Oleg Nesterov wrote: > > > > > > > > Sadly, you can't use srcu/qrcu because it doesn't handle timeouts. > > > > > > Interesting... So the thought is to have a synchronize_srcu_timeout() > > > or something similar that waited for a grace period to elapse or for > > > a timeout to expire, whichever comes first? It should not be too hard > > > to arrange something, if needed. > > > > Yes. As for qrcu (see http://marc.info/?t=116484476500001), I think it is easy. > > First, we add "int interrupted" into struct qrcu_struct, then something like this > > Even simpler, we don't need ->interrupted. I have to ask... What sorts of performance characteristics are needed here? The reason that I ask is because putting a straight synchronize_qrcu() into a workqueue (or something similar) and then using a timer to provide any needed wakeup seems a lot simpler than rearranging the innards of synchronize_qrcu(). (Yes, I am feeling cowardly. Why do you ask?) Thanx, Paul > long synchronize_qrcu_timeout(struct qrcu_struct *qp, long tout) > { > int idx, prv; > > smp_mb(); > mutex_lock(&qp->mutex); > > idx = qp->completed & 0x1; > prv = idx ^ 0x1; > > if (unlikely(atomic_read(qp->ctr + prv))) { > // the previous call has not succeed, > // finish the wait > __wait_event_timeout(qp->wq, !atomic_read(qp->ctr + prv), tout); > if (unlikely(!tout)) > goto out; > } > > if (atomic_read(qp->ctr + idx) == 1) > goto out; > > atomic_inc(qp->ctr + prv); > qp->completed++; > > atomic_dec(qp->ctr + idx); > __wait_event_timeout(qp->wq, !atomic_read(qp->ctr + idx), tout); > out: > mutex_unlock(&qp->mutex); > smp_mb(); > > return tout; > } > > Oleg. > > - > 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/ > - 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/