netdev - Re: [PATCH] virtio_net: Remove BUG() to aviod machine dead

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Date:   Wed, 2 Jun 2021 08:59:26 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jason Wang <jasowang@...hat.com>
Cc:     Xianting Tian <xianting.tian@...ux.alibaba.com>,
        "Michael S. Tsirkin" <mst@...hat.com>, davem@...emloft.net,
        kuba@...nel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_net: Remove BUG() to aviod machine dead

On Tue, May 25, 2021 at 02:19:03PM +0800, Jason Wang wrote:
> 
> 在 2021/5/19 下午10:18, Xianting Tian 写道:
> > thanks, I submit the patch as commented by Andrew
> > https://lkml.org/lkml/2021/5/18/256
> > 
> > Actually, if xmit_skb() returns error, below code will give a warning
> > with error code.
> > 
> >     /* Try to transmit */
> >     err = xmit_skb(sq, skb);
> > 
> >     /* This should not happen! */
> >     if (unlikely(err)) {
> >         dev->stats.tx_fifo_errors++;
> >         if (net_ratelimit())
> >             dev_warn(&dev->dev,
> >                  "Unexpected TXQ (%d) queue failure: %d\n",
> >                  qnum, err);
> >         dev->stats.tx_dropped++;
> >         dev_kfree_skb_any(skb);
> >         return NETDEV_TX_OK;
> >     }
> > 
> > 
> > 
> > 
> > 
> > 在 2021/5/18 下午5:54, Michael S. Tsirkin 写道:
> > > typo in subject
> > > 
> > > On Tue, May 18, 2021 at 05:46:56PM +0800, Xianting Tian wrote:
> > > > When met error, we output a print to avoid a BUG().
> 
> 
> So you don't explain why you need to remove BUG(). I think it deserve a
> BUG().

BUG() will crash the machine and virtio_net is not kernel core
functionality that must stop the machine to prevent anything truly
harmful and basic.

I would argue that code in drivers/* shouldn't call BUG() macros at all.

If it is impossible, don't check for that or add WARN_ON() and recover,
but don't crash whole system.

Thanks