Return-path: Received: from lanfw001a.cxnet.dk ([87.72.215.196]:51190 "EHLO lanfw001a.cxnet.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752154AbZFXLcQ (ORCPT ); Wed, 24 Jun 2009 07:32:16 -0400 Subject: Re: [PATCH 03/10] mac80211: Use rcu_barrier() on unload. From: Jesper Dangaard Brouer To: Johannes Berg 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, yoshfuji@linux-ipv6.org, shemminger@linux-foundation.org, linux-nfs@vger.kernel.org, bfields@fieldses.org, neilb@suse.de, linux-ext4@vger.kernel.org, tytso@mit.edu, adilger@sun.com, netfilter-devel@vger.kernel.org In-Reply-To: <1245838862.21314.48.camel@johannes.local> References: <20090623150330.22490.87327.stgit@localhost> <20090623150409.22490.99106.stgit@localhost> <1245770155.21314.38.camel@johannes.local> <1245837965.6695.45.camel@localhost.localdomain> <1245838862.21314.48.camel@johannes.local> Content-Type: text/plain Date: Wed, 24 Jun 2009 13:32:17 +0200 Message-Id: <1245843137.6695.48.camel@localhost.localdomain> Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Wed, 2009-06-24 at 12:21 +0200, Johannes Berg wrote: > On Wed, 2009-06-24 at 12:06 +0200, Jesper Dangaard Brouer wrote: > > On Tue, 2009-06-23 at 17:15 +0200, Johannes Berg wrote: > > > On Tue, 2009-06-23 at 17:04 +0200, Jesper Dangaard Brouer wrote: > > > > The mac80211 module uses rcu_call() thus it should use rcu_barrier() > > > > on module unload. > > > > > > > > I'm having a hardtime verifying that no more call_rcu() callbacks can > > > > be schedules in the module unload path. Could a maintainer please > > > > look into this? > > > > > > > > Signed-off-by: Jesper Dangaard Brouer > > > > --- > > > > > > > > net/mac80211/main.c | 2 ++ > > > > 1 files changed, 2 insertions(+), 0 deletions(-) > > > > > > > > diff --git a/net/mac80211/main.c b/net/mac80211/main.c > > > > index 092a017..e9f70ce 100644 > > > > --- a/net/mac80211/main.c > > > > +++ b/net/mac80211/main.c > > > > @@ -1100,6 +1100,8 @@ static void __exit ieee80211_exit(void) > > > > ieee80211s_stop(); > > > > > > > > ieee80211_debugfs_netdev_exit(); > > > > + > > > > + rcu_barrier(); /* Wait for completion of call_rcu()'s */ > > > > } > > > > > > I don't think this is correct at all -- note that call_rcu() is done in > > > some of the mesh code, so I would think you need to do this in > > > ieee80211_stop() since the call_rcu() code requires the interface to > > > still be around. And when it's stopped everything should be idle. > > > > Should it then not be in mesh.c ieee80211_stop_mesh(). We can replace > > the synchronize_rcu() in this function with a rcu_barrier(). > > Yes, this seems correct. > > johannes Can I consider this a: Acked-by: Johannes Berg ??? DaveM seems to like this as patchwork.ozlabs.org picks up this automatically... -- Med venlig hilsen / Best regards Jesper Brouer ComX Networks A/S Linux Network developer Cand. Scient Datalog / MSc. Author of http://adsl-optimizer.dk LinkedIn: http://www.linkedin.com/in/brouer