netdev - Re: [PATCH net v3] net: mctp: Fix tx queue stall

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Message-ID: <eab5b41703789ae545e744c2df8ae44d884b43d0.camel@codeconstruct.com.au>
Date: Wed, 29 Oct 2025 16:26:08 +0800
From: Jeremy Kerr <jk@...econstruct.com.au>
To: Jinliang Wang <jinliangw@...gle.com>, Matt Johnston
	 <matt@...econstruct.com.au>, netdev@...r.kernel.org
Cc: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>,  Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3] net: mctp: Fix tx queue stall

Hi Jinliang,

> The tx queue can become permanently stuck in a stopped state due to a
> race condition between the URB submission path and its completion
> callback.
> 
> The URB completion callback can run immediately after usb_submit_urb()
> returns, before the submitting function calls netif_stop_queue(). If
> this occurs, the queue state management becomes desynchronized, leading
> to a stall where the queue is never woken.
> 
> Fix this by moving the netif_stop_queue() call to before submitting the
> URB. This closes the race window by ensuring the network stack is aware
> the queue is stopped before the URB completion can possibly run.

Thanks!

Acked-by: Jeremy Kerr <jk@...econstruct.com.au>

Cheers,


Jeremy