Date: Wed, 4 Jun 2014 10:35:31 -0500 From: Bryan Venteicher <bryanv@freebsd.org> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: jfv@freebsd.org, Bryan Venteicher <bryanv@freebsd.org>, current@freebsd.org, stefanogarzarella@gmail.com Subject: Re: BUG: some drivers return ENOBUFS when the mbuf is actually queued Message-ID: <CAGaYwLdL50y9iMs5mzy-rqUoFrB05SWHqEctfwJUTwcd3QPCBg@mail.gmail.com> In-Reply-To: <20140604134945.GA64688@onelab2.iet.unipi.it> References: <20140604134945.GA64688@onelab2.iet.unipi.it>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, Jun 4, 2014 at 8:49 AM, Luigi Rizzo <rizzo@iet.unipi.it> wrote: > Hi, > if I read correctly the code, there are a few network device drivers > (igb, ixgbe, i40e, vtnet, vmxnet) where ifp->if_transmit(ifp, m) > can return ENOBUFS even when 'm' has _not_ been dropped: > > e1000/if_igb.c :: igb_mq_start() > can return ENOBUFS from igb_xmit() > > ixgbe/ixgbe_main.c :: ixgbe_mq_start_locked() > can return ENOBUFS from ixgbe_xmit() > (similar for i40) > > virtio/network/if_vtnet.c :: vtnet_txq_mq_start > can return ENOBUFS if virtqueue_full() > > In all these cases, the error comes from a later attempt to transfer > mbufs from the buf_ring to the NIC ring. > > All drivers using if_transmit() seem correct, as well as a bunch > of others (cxgbe, sfxge, mxge ...) that reassign if_transmit and I > checked for correctness. > > I think that when the current buffer has been queued, returning > ENOBUFS is extremely confusing and should not be done. > > I would also argue that the return from ifp->if_transmit(ifp, m) > should only tell what happened to 'm', not other things > such as the status of the queue. > > Any objections if i fix the above drivers ? > > No objection for vtnet and vmxnet. > cheers > luigi > > (For those curious: i found this issue when using emulated > netmap mode on top of a standard driver. The netmap emulation > code assumes that ENOBUFS indicates that the driver has > m_free()'d the mbuf, same as it happens on linux, and the > bug was causing panics in my system). > >
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAGaYwLdL50y9iMs5mzy-rqUoFrB05SWHqEctfwJUTwcd3QPCBg>