netdev - Re: [PATCH v4 1/4] virtio-net: disable delayed refill when pausing rx

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Message-ID: <CACGkMEt5=r_JbfHeU=dpk20F5uE6TJouTPdKUUScYtQGfAw1tg@mail.gmail.com>
Date: Mon, 21 Apr 2025 11:03:38 +0800
From: Jason Wang <jasowang@...hat.com>
To: Bui Quang Minh <minhquangbui99@...il.com>
Cc: virtualization@...ts.linux.dev, "Michael S. Tsirkin" <mst@...hat.com>, 
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Jesper Dangaard Brouer <hawk@...nel.org>, John Fastabend <john.fastabend@...il.com>, 
	Eugenio Pérez <eperezma@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	bpf@...r.kernel.org
Subject: Re: [PATCH v4 1/4] virtio-net: disable delayed refill when pausing rx

On Thu, Apr 17, 2025 at 3:29 PM Bui Quang Minh <minhquangbui99@...il.com> wrote:
>
> When pausing rx (e.g. set up xdp, xsk pool, rx resize), we call
> napi_disable() on the receive queue's napi. In delayed refill_work, it
> also calls napi_disable() on the receive queue's napi.  When
> napi_disable() is called on an already disabled napi, it will sleep in
> napi_disable_locked while still holding the netdev_lock. As a result,
> later napi_enable gets stuck too as it cannot acquire the netdev_lock.
> This leads to refill_work and the pause-then-resume tx are stuck
> altogether.
>
> This scenario can be reproducible by binding a XDP socket to virtio-net
> interface without setting up the fill ring. As a result, try_fill_recv
> will fail until the fill ring is set up and refill_work is scheduled.
>
> This commit adds virtnet_rx_(pause/resume)_all helpers and fixes up the
> virtnet_rx_resume to disable future and cancel all inflights delayed
> refill_work before calling napi_disable() to pause the rx.
>
> Fixes: 413f0271f396 ("net: protect NAPI enablement with netdev_lock()")
> Acked-by: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Bui Quang Minh <minhquangbui99@...il.com>

Acked-by: Jason Wang <jasowang@...hat.com>

(In the future, we may consider switch to per virtqueue refill work instead)

Thanks