From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: [PATCH alt.2] af_packet: Don't use skb after dev_queue_xmit() Date: Wed, 6 Jan 2010 09:15:32 +0000 Message-ID: <20100106091532.GA10201@ff.dom.local> References: <20100105230746.GA6612@del.dom.local> <4B43F72C.9090004@majjas.com> <20100106072208.GA6711@ff.dom.local> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , shemminger@linux-foundation.org, akpm@linux-foundation.org, flyboy@gmail.com, linux-kernel@vger.kernel.org, netdev@vger.kernel.org To: Michael Breuer Return-path: Content-Disposition: inline In-Reply-To: <20100106072208.GA6711@ff.dom.local> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Wed, Jan 06, 2010 at 07:22:08AM +0000, Jarek Poplawski wrote: > On Tue, Jan 05, 2010 at 09:36:28PM -0500, Michael Breuer wrote: > > Is it possible that this patch is causing the transmission to > > momentarily halt such that the overall utilization appears low at the > > time I see the interrupt errors, vs. the other patch which perhaps > > doesn't interrupt the traffic flow quite so much? > > Yes, without this patch xmit could be stopped earlier on some kind of > errors, with retransmit of the last message possible. On the other > hand, other dev_queue_xmit() (negative) errors, are ignored. So this > place could be still improved by adding proper err handling (or > removing getting err return from dev_queue_xmit() at all). On the other hand, returning just this one net_xmit_errno() would be consistent with non-MMAP sendmsg, so here is an alternative version for testing. Thanks, Jarek P. -----------------> (alternative #2) tpacket_snd() can change and kfree an skb after dev_queue_xmit(), which is illegal. With debugging by: Stephen Hemminger Reported-by: Michael Breuer Signed-off-by: Jarek Poplawski --- net/packet/af_packet.c | 8 +++----- 1 files changed, 3 insertions(+), 5 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index e0516a2..aba2049 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1021,9 +1021,10 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) status = TP_STATUS_SEND_REQUEST; err = dev_queue_xmit(skb); - if (unlikely(err > 0 && (err = net_xmit_errno(err)) != 0)) - goto out_xmit; packet_increment_head(&po->tx_ring); + if (unlikely(err > 0 && (err = net_xmit_errno(err)) != 0)) + goto out_put; + len_sum += tp_len; } while (likely((ph != NULL) || ((!(msg->msg_flags & MSG_DONTWAIT)) && @@ -1033,9 +1034,6 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg) err = len_sum; goto out_put; -out_xmit: - skb->destructor = sock_wfree; - atomic_dec(&po->tx_ring.pending); out_status: __packet_set_status(po, ph, status); kfree_skb(skb);