On Fri, 11 Jun 2010 04:33:43 am Michael S. Tsirkin wrote:
> > > > @@ -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);
...
>
> Well, I only keep the existing behaviour around.
Actually, it *does* change behavior, as the comment indicates. So let's
fix the whole thing. AFAICT wth TX_BUSY we'll get called again RSN, and
that's not really useful for OOM.
This is what I have:
Subject: virtio_net: fix oom handling on tx
Date: Thu, 10 Jun 2010 18:20:41 +0300
From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
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 <mst@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> (...and avoid TX_BUSY)
Cc: stable@xxxxxxxxxx
---
drivers/net/virtio_net.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -562,7 +562,6 @@ static netdev_tx_t start_xmit(struct sk_
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);
@@ -571,14 +570,17 @@ 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;
+ kfree_skb(skb);
+ return NETDEV_TX_OK;
}
virtqueue_kick(vi->svq);
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