Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759128Ab0FJRRp (ORCPT ); Thu, 10 Jun 2010 13:17:45 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:33936 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751610Ab0FJRRo (ORCPT ); Thu, 10 Jun 2010 13:17:44 -0400 Subject: Re: [PATCH for-2.6.35] virtio_net: fix oom handling on tx From: Sridhar Samudrala To: "Michael S. Tsirkin" Cc: virtualization@lists.linux-foundation.org, Rusty Russell , Jiri Pirko , Shirley Ma , netdev@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20100610152041.GA3480@redhat.com> References: <20100610152041.GA3480@redhat.com> Content-Type: text/plain Date: Thu, 10 Jun 2010 10:17:07 -0700 Message-Id: <1276190227.22064.19.camel@w-sridhar.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2072 Lines: 60 On Thu, 2010-06-10 at 18:20 +0300, Michael S. Tsirkin wrote: > virtio net will never try to overflow the TX ring, so the only reason > add_buf may fail is out of memory. Thus, we can not stop the > device until some request completes - there's no guarantee anything > at all is outstanding. > > Make the error message clearer as well: error here does not > indicate queue full. > > Signed-off-by: Michael S. Tsirkin > --- > drivers/net/virtio_net.c | 15 ++++++++------- > 1 files changed, 8 insertions(+), 7 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 85615a3..e48a06f 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -563,7 +563,6 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev) > struct virtnet_info *vi = netdev_priv(dev); > int capacity; > > -again: > /* Free up any pending old buffers before queueing new ones. */ > free_old_xmit_skbs(vi); > > @@ -572,12 +571,14 @@ again: > > /* This can happen with OOM and indirect buffers. */ > if (unlikely(capacity < 0)) { > - netif_stop_queue(dev); > - dev_warn(&dev->dev, "Unexpected full queue\n"); > - if (unlikely(!virtqueue_enable_cb(vi->svq))) { > - virtqueue_disable_cb(vi->svq); > - netif_start_queue(dev); > - goto again; > + if (net_ratelimit()) { > + if (likely(capacity == -ENOMEM)) > + dev_warn(&dev->dev, > + "TX queue failure: out of memory\n"); > + else > + dev_warn(&dev->dev, > + "Unexpected TX queue failure: %d\n", > + capacity); > } > return NETDEV_TX_BUSY; > } It is not clear to me how xmit_skb() can return -ENOMEM. xmit_skb() calls virtqueue_add_buf_gfp() which can return -ENOSPC. Even vring_add_indirect() doesn't return -ENOMEM on kmalloc failure. Thanks Sridhar -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/