From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next] packet: Protect packet sk list with mutex Date: Mon, 20 Aug 2012 17:11:40 +0200 Message-ID: <1345475500.5158.321.camel@edumazet-glaptop> References: <50324EBC.9060804@parallels.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: David Miller , Linux Netdev List To: Pavel Emelyanov Return-path: Received: from mail-bk0-f46.google.com ([209.85.214.46]:41249 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756790Ab2HTPLp (ORCPT ); Mon, 20 Aug 2012 11:11:45 -0400 Received: by bkwj10 with SMTP id j10so1891160bkw.19 for ; Mon, 20 Aug 2012 08:11:44 -0700 (PDT) In-Reply-To: <50324EBC.9060804@parallels.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2012-08-20 at 18:50 +0400, Pavel Emelyanov wrote: > In patch eea68e2f (packet: Report socket mclist info via diag module) I've > introduced a "scheduling in atomic" problem in packet diag module -- the > socket list is traversed under rcu_read_lock() while performed under it sk > mclist access requires rtnl lock (i.e. -- mutex) to be taken. Similar thing > was then re-introduced by further packet diag patches (fanount mutex and > pgvec mutex for rings) :( > > Apart from being terribly sorry for the above, I propose to change the > packet sk list protection from spinlock to mutex. This lock currently > protects only the sklist modifications (that already happen in sleeping > context) and nothing more. > > Am I wrong again and a fine-grained atomic locking is required for > everything that is reported by packet diag instead? > > Signed-off-by: Pavel Emelyanov > > --- > > diff --git a/include/net/netns/packet.h b/include/net/netns/packet.h > index cb4e894..4780b08 100644 > --- a/include/net/netns/packet.h > +++ b/include/net/netns/packet.h > @@ -8,7 +8,7 @@ > #include > > struct netns_packet { > - spinlock_t sklist_lock; > + struct mutex sklist_lock; > struct hlist_head sklist; > }; > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > index 226b2cd..5048672 100644 > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -2308,10 +2308,10 @@ static int packet_release(struct socket *sock) > net = sock_net(sk); > po = pkt_sk(sk); > > - spin_lock_bh(&net->packet.sklist_lock); > + mutex_lock(&net->packet.sklist_lock); > sk_del_node_init_rcu(sk); > sock_prot_inuse_add(net, sk->sk_prot, -1); Last time I checked, sock_prot_inuse_add() needed BH protection. ( This could be relaxed somehow on x86 thanks to this_cpu_add() ... but thats another point) Could you please report the full stack trace ?