From: Johannes Berg Subject: Re: [PATCH 03/10] mac80211: Use rcu_barrier() on unload. Date: Wed, 24 Jun 2009 12:21:02 +0200 Message-ID: <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> Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-pZJIqGJkvSCF73OGmZi0" 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 To: Jesper Dangaard Brouer Return-path: In-Reply-To: <1245837965.6695.45.camel@localhost.localdomain> Sender: linux-ext4-owner@vger.kernel.org List-ID: --=-pZJIqGJkvSCF73OGmZi0 Content-Type: text/plain Content-Transfer-Encoding: quoted-printable 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. > > >=20 > > > 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? > > >=20 > > > Signed-off-by: Jesper Dangaard Brouer > > > --- > > >=20 > > > net/mac80211/main.c | 2 ++ > > > 1 files changed, 2 insertions(+), 0 deletions(-) > > >=20 > > > 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(); > > > =20 > > > ieee80211_debugfs_netdev_exit(); > > > + > > > + rcu_barrier(); /* Wait for completion of call_rcu()'s */ > > > } > >=20 > > 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. >=20 > 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 --=-pZJIqGJkvSCF73OGmZi0 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQIcBAABAgAGBQJKQf4JAAoJEODzc/N7+QmayVkP/j1S2XEXRYf5Yd3tTJcNqNkB 3C4YvnUxNNwO6Uk17Y6NCkZ7SblzrIpxHKh5588Vtfcq8GE+aeKzS1F64kDqw+az 846Y++wS2liZTJ67PfoDc33HGBQBtFSnTZOpC86j2RCGv4fDV0T5VQkVSupA6UdW H5FpuBHlKPgkvkHoa62gth3FNUGSG7MFDqpUwk/WiOigewb3e2W57C6i6qzNL5Iz nt7eqLeSnQX59e2w9w+inwtflU/bu5OGqQGekMBj4wZKYinLzp2UOEfxW5KENG+a ANOEznwgo5UvOOXQj+pwQaF+ZvHh3BttfjR4tKmMAc494QcvrDab8TvGNUKwHOFE xomJZYO6iTifankWA5/1q6yYnf2wPHBia9ov0oysIAI4G0XP7S8hkAswg+/uQMMe TFP96Z75XDn3eBbHi7h1TcycKt5Vtd+G7Wqg/aZ6W8h5PLBCeOo1OAz654bRyIGB VbVg50O2WQeD/2MTLfnf6XKLYN7YaBvB9SFURpeJnVHaO4aQ+ziPNPBO8KQi4yD1 5kSpVez9ZoftOWf62Xz12xjdtgahmAqeugQR9ziNyv5XjnbpE7sQWiABtiF9F62N y0QjtstgnOSM6CGiIEVb2eZehIp6w3AK78RLMeb5/3KU+/6m6N6oGptZTyXxib+d yl4FzVQ1fHXT6uqZ4PhE =8doT -----END PGP SIGNATURE----- --=-pZJIqGJkvSCF73OGmZi0--