linux-kernel - Re: [PATCH net] virtio_net: adjust the execution order of function `virtnet

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Message-ID: <20250818083917.435a4263@kernel.org>
Date: Mon, 18 Aug 2025 08:39:17 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Junnan Wu <junnan01.wu@...sung.com>
Cc: andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
 eperezma@...hat.com, jasowang@...hat.com, lei19.wang@...sung.com,
 linux-kernel@...r.kernel.org, mst@...hat.com, netdev@...r.kernel.org,
 pabeni@...hat.com, q1.huang@...sung.com, virtualization@...ts.linux.dev,
 xuanzhuo@...ux.alibaba.com, ying123.xu@...sung.com
Subject: Re: [PATCH net] virtio_net: adjust the execution order of function
 `virtnet_close` during freeze

On Mon, 18 Aug 2025 09:15:22 +0800 Junnan Wu wrote:
> > > Yes, you are right. The commit of this fix tag is the first commit I
> > > found which add function `virtnet_poll_cleantx`. Actually, we are not
> > > sure whether this issue appears after this commit.
> > > 
> > > In our side, this issue is found by chance in version 5.15.
> > > 
> > > It's hard to find the key commit which cause this issue
> > > for reason that the reproduction of this scenario is too complex.  
> > 
> > I think the problem needs to be more clearly understood, and then it
> > will be easier to find the fixes tag. At the face of it the patch
> > makes it look like close() doesn't reliably stop the device, which
> > is highly odd.  
> 
> Yes, you are right. It is really strange that `close()` acts like
> that, because current order has worked for long time. But panic call
> stack in our env shows that the function `virtnet_close` and
> `netif_device_detach` should have a correct execution order. And it
> needs more time to find the fixes tag. I wonder that is it must have
> fixes tag to merge?
> 
> By the way, you mentioned that "the problem need to be more clearly
> understood", did you mean the descriptions and sequences in commit
> message are not easy to understand? Do you have some suggestions
> about this?

Perhaps Jason gets your explanation and will correct me, but to me it
seems like the fix is based on trial and error rather than clear
understanding of the problem. If you understood the problem clearly
you should be able to find the Fixes tag without a problem..