Messages in this thread | | | Date | Tue, 03 Nov 2009 13:14:06 -0500 | From | Gregory Haskins <> | Subject | Re: [PATCHv7 3/3] vhost_net: a kernel-level virtio server |
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Gregory Haskins wrote: > Eric Dumazet wrote: >> Michael S. Tsirkin a écrit : >>> +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) >> > > > Michael, > I warned you that this needed better documentation ;) > > Eric, > I think I flagged this once before, but Michael convinced me that it > was indeed "ok", if but perhaps a bit unconventional. I will try to > find the thread. > > Kind Regards, > -Greg >
Here it is:
http://lkml.org/lkml/2009/8/12/173
Kind Regards, -Greg
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