linux-kernel - Re: [PATCH] net: usbnet: Avoid potential RCU stall on LINK

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Message-ID: <20250714163505.44876e62@kernel.org>
Date: Mon, 14 Jul 2025 16:35:05 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: John Ernberg <john.ernberg@...ia.se>
Cc: Oliver Neukum <oneukum@...e.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Ming Lei
 <ming.lei@...onical.com>, "netdev@...r.kernel.org"
 <netdev@...r.kernel.org>, "linux-usb@...r.kernel.org"
 <linux-usb@...r.kernel.org>, "linux-kernel@...r.kernel.org"
 <linux-kernel@...r.kernel.org>, "stable@...r.kernel.org"
 <stable@...r.kernel.org>
Subject: Re: [PATCH] net: usbnet: Avoid potential RCU stall on LINK_CHANGE
 event

On Thu, 10 Jul 2025 08:50:40 +0000 John Ernberg wrote:
> Having a Gemalto Cinterion PLS83-W modem attached to USB and activating the
> cellular data link would sometimes yield the following RCU stall, leading
> to a system freeze:

Do you know which sub-driver it's using?
I'm worried that this is still racy.
Since usbnet_bh checks if carrier is ok and __handle_link_change()
checks the opposite something must be out of sync if both run.
Most likely something restored the carrier while we're still handling
the previous carrier loss.
-- 
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