From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id C0D5D6B006A for ; Tue, 3 Nov 2009 13:04:19 -0500 (EST) Message-ID: <4AF0708B.4020406@gmail.com> Date: Tue, 03 Nov 2009 19:03:55 +0100 From: Eric Dumazet MIME-Version: 1.0 Subject: Re: [PATCHv7 3/3] vhost_net: a kernel-level virtio server References: <20091103172422.GD5591@redhat.com> In-Reply-To: <20091103172422.GD5591@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org To: "Michael S. Tsirkin" Cc: netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@elte.hu, linux-mm@kvack.org, akpm@linux-foundation.org, hpa@zytor.com, gregory.haskins@gmail.com, Rusty Russell , s.hetze@linux-ag.com, "Paul E. McKenney" List-ID: Michael S. Tsirkin a ecrit : > +static void handle_tx(struct vhost_net *net) > +{ > + struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_TX]; > + unsigned head, out, in, s; > + struct msghdr msg = { > + .msg_name = NULL, > + .msg_namelen = 0, > + .msg_control = NULL, > + .msg_controllen = 0, > + .msg_iov = vq->iov, > + .msg_flags = MSG_DONTWAIT, > + }; > + size_t len, total_len = 0; > + int err, wmem; > + size_t hdr_size; > + struct socket *sock = rcu_dereference(vq->private_data); > + if (!sock) > + return; > + > + wmem = atomic_read(&sock->sk->sk_wmem_alloc); > + if (wmem >= sock->sk->sk_sndbuf) > + return; > + > + use_mm(net->dev.mm); > + mutex_lock(&vq->mutex); > + vhost_no_notify(vq); > + using rcu_dereference() and mutex_lock() at the same time seems wrong, I suspect that your use of RCU is not correct. 1) rcu_dereference() should be done inside a read_rcu_lock() section, and we are not allowed to sleep in such a section. (Quoting Documentation/RCU/whatisRCU.txt : It is illegal to block while in an RCU read-side critical section, ) 2) mutex_lock() can sleep (ie block) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org