Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967558AbXHGWDv (ORCPT ); Tue, 7 Aug 2007 18:03:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S937521AbXHGViG (ORCPT ); Tue, 7 Aug 2007 17:38:06 -0400 Received: from x346.tv-sign.ru ([89.108.83.215]:35298 "EHLO mail.screens.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937512AbXHGViE (ORCPT ); Tue, 7 Aug 2007 17:38:04 -0400 Date: Wed, 8 Aug 2007 01:37:49 +0400 From: Oleg Nesterov To: Trond Myklebust Cc: Neil Brown , Andrew Morton , Marc Dietrich , Johannes Berg , nfs@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [NFS] 2.6.23-rc1-mm2 Message-ID: <20070807213749.GA461@tv-sign.ru> References: <20070731230932.a9459617.akpm@linux-foundation.org> <200708031301.01569.marc.dietrich@ap.physik.uni-giessen.de> <20070803093830.39852a01.akpm@linux-foundation.org> <1186160608.7255.10.camel@localhost> <20070803172137.GA3783@tv-sign.ru> <1186520929.6625.12.camel@heimdal.trondhjem.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1186520929.6625.12.camel@heimdal.trondhjem.org> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1821 Lines: 49 On 08/07, Trond Myklebust wrote: > > On Fri, 2007-08-03 at 21:21 +0400, Oleg Nesterov wrote: > > On 08/03, Trond Myklebust wrote: > > > I'll have a look at this. I suspect that most if not all of our calls to > > > run_workqueue()/flush_scheduled_work() can now be replaced by more > > > targeted calls to cancel_work_sync() and cancel_delayed_work_sync(). > > > > Yes, please, if possible. > > All the NFS and SUNRPC cases appear to be trivial. IOW: the only reason > for the flush_workqueue()/flush_scheduled_work() calls was to ensure > that the cancel_work()/cancel_delayed_work() calls preceding them have > completed. Nevertheless I've split the conversion into two patches, > since one touches only the NFS code, whereas the other touches the > SUNRPC client and server code. > > The two patches have been tested, and appear to work... Great! > void > nfs4_kill_renewd(struct nfs_client *clp) > { > down_read(&clp->cl_sem); > - cancel_delayed_work(&clp->cl_renewd); > + cancel_delayed_work_sync(&clp->cl_renewd); > up_read(&clp->cl_sem); > - flush_scheduled_work(); > } this looks unsafe to me, the window is very small, but afaics this can deadlock if called when nfs4_renew_state() has already started, but didn't take ->cl_sem yet. Can't we avoid taking clp->cl_sem here? Btw, unless I missed something, the code without this patch looks incorrect too: cancel_delayed_work() can fail if the timer expired, but the ->cl_renewd didn't run yet. In that case nfs4_renew_state() can run and re-schedule itself after flush_scheduled_work() returns. 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/