From: Jakub Kicinski <kuba@kernel.org>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Yunsheng Lin <linyunsheng@huawei.com>,
Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
Jason Wang <jasowang@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
virtualization@lists.linux-foundation.org, bpf@vger.kernel.org,
Yichun Zhang <yichun@openresty.com>,
Alexander Duyck <alexanderduyck@fb.com>,
netdev@vger.kernel.org
Subject: Re: [PATCH net, stable v1 3/3] virtio_net: add checking sq is full inside xdp xmit
Date: Wed, 8 Mar 2023 22:51:40 -0800 [thread overview]
Message-ID: <20230308225140.46c22c89@kernel.org> (raw)
In-Reply-To: <20230308071921-mutt-send-email-mst@kernel.org>
On Wed, 8 Mar 2023 07:21:07 -0500 Michael S. Tsirkin wrote:
> > > * netdev_tx_t (*ndo_start_xmit)(struct sk_buff *skb,
> > > * struct net_device *dev);
> > > * Called when a packet needs to be transmitted.
> > > * Returns NETDEV_TX_OK. Can return NETDEV_TX_BUSY, but you should stop
> > > * the queue before that can happen; it's for obsolete devices and weird
> > > * corner cases, but the stack really does a non-trivial amount
> > > * of useless work if you return NETDEV_TX_BUSY.
> > > * Required; cannot be NULL.
> >
> > Thanks for the pointer. It is intersting, it seems most driver is not flollowing
> > the suggestion.
>
> Yes - I don't know why.
Most modern drivers don't stop the queue upfront?
We try to catch it in review, so anything remotely recent should.
But a lot of people DTRT *and* check at the start of .xmit if
the skb fits (return BUSY if it doesn't) - defensive programming.
But the BUSY path should never hit.
next prev parent reply other threads:[~2023-03-09 6:51 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-08 2:49 [PATCH net, stable v1 0/3] add checking sq is full inside xdp xmit Xuan Zhuo
2023-03-08 2:49 ` [PATCH net, stable v1 1/3] virtio_net: reorder some funcs Xuan Zhuo
2023-03-08 5:20 ` Jason Wang
2023-03-08 6:53 ` Michael S. Tsirkin
2023-03-08 2:49 ` [PATCH net, stable v1 2/3] virtio_net: separate the logic of checking whether sq is full Xuan Zhuo
2023-03-08 5:20 ` Jason Wang
2023-03-08 2:49 ` [PATCH net, stable v1 3/3] virtio_net: add checking sq is full inside xdp xmit Xuan Zhuo
2023-03-08 5:20 ` Jason Wang
2023-03-08 6:59 ` Yunsheng Lin
2023-03-08 7:14 ` Xuan Zhuo
2023-03-08 8:13 ` Yunsheng Lin
2023-03-08 12:21 ` Michael S. Tsirkin
2023-03-09 1:49 ` Yunsheng Lin
2023-03-09 6:51 ` Jakub Kicinski [this message]
2023-03-11 0:50 ` [PATCH net, stable v1 0/3] " patchwork-bot+netdevbpf
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