netdev - Re: virtio_close() stuck on napi_disable

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Message-ID: <20250722145524.7ae61342@kernel.org>
Date: Tue, 22 Jul 2025 14:55:24 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Paolo Abeni <pabeni@...hat.com>, Zigit Zo <zuozhijie@...edance.com>
Cc: "Michael S. Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Eugenio Pérez
 <eperezma@...hat.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: virtio_close() stuck on napi_disable_locked()

On Tue, 22 Jul 2025 13:00:14 +0200 Paolo Abeni wrote:
> Hi,
> 
> The NIPA CI is reporting some hung-up in the stats.py test caused by the
> virtio_net driver stuck at close time.
> 
> A sample splat is available here:
> 
> https://netdev-3.bots.linux.dev/vmksft-drv-hw-dbg/results/209441/4-stats-py/stderr
> 
> AFAICS the issue happens only on debug builds.
> 
> I'm wild guessing to something similar to the the issue addressed by
> commit 4bc12818b363bd30f0f7348dd9ab077290a637ae, possibly for tx_napi,
> but I could not spot anything obvious.
> 
> Could you please have a look?

It only hits in around 1 in 5 runs. Likely some pre-existing race, but
it started popping up for us when be5dcaed694e ("virtio-net: fix
recursived rtnl_lock() during probe()") was merged. It never hit before.
If we can't find a quick fix I think we should revert be5dcaed694e for
now, so that it doesn't end up regressing 6.16 final.