From: Theodore Tso Subject: Re: [PATCH 01/10] ext4: Use rcu_barrier() on module unload. Date: Sun, 5 Jul 2009 22:31:13 -0400 Message-ID: <20090706023113.GE6706@mit.edu> References: <20090623150330.22490.87327.stgit@localhost> <20090623150358.22490.24818.stgit@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , "Paul E. McKenney" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dougthompson@xmission.com, bluesmoke-devel@lists.sourceforge.net, axboe@kernel.dk, Patrick McHardy , christine.caulfield@googlemail.com, Trond.Myklebust@netapp.com, linux-wireless@vger.kernel.org, johannes@sipsolutions.net, yoshfuji@linux-ipv6.org, shemminger@linux-foundation.org, linux-nfs@vger.kernel.org, bfields@fieldses.org, neilb@suse.de, linux-ext4@vger.kernel.org, adilger-xsfywfwIY+M@public.gmane.org, netfilter-devel@vger.kernel.org To: Jesper Dangaard Brouer Return-path: Received: from thunk.org ([69.25.196.29]:42602 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753973AbZGFCcP (ORCPT ); Sun, 5 Jul 2009 22:32:15 -0400 In-Reply-To: <20090623150358.22490.24818.stgit@localhost> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Tue, Jun 23, 2009 at 05:03:59PM +0200, Jesper Dangaard Brouer wrote: > The ext4 module uses rcu_call() thus it should use rcu_barrier()on > module unload. > > The kmem cache ext4_pspace_cachep is sometimes free'ed using > call_rcu() callbacks. Thus, we must wait for completion of call_rcu() > before doing kmem_cache_destroy(). > > I have difficult determining if no new call_rcu() callbacks can be envoked. > Would the maintainer please verify this? Yes, that's correct. Thanks; I've included this in the ext4 patch queue. - Ted