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Date: Thu, 6 Jun 2024 08:46:58 -0700
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Subject: Re: [PATCH] igb: Fix igb_down hung on surprise removal
To: Ying Hsu <yinghsu@chromium.org>
Cc: netdev@vger.kernel.org, grundler@chromium.org,
 "David S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>,
 Jakub Kicinski <kuba@kernel.org>,
 Jesse Brandeburg <jesse.brandeburg@intel.com>,
 Paolo Abeni <pabeni@redhat.com>, Tony Nguyen <anthony.l.nguyen@intel.com>,
 intel-wired-lan@lists.osuosl.org, linux-kernel@vger.kernel.org
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From: Stefan Schaeckeler <schaecsn@gmx.net>
In-Reply-To: <CAAa9mD1HGJDKzoLoqZzyrR5wsk_6voWs+VmoZoo9ZontyvjUww@mail.gmail.com>
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Hello Ying,

On 6/6/24 01:03, Ying Hsu wrote:
> On the CalDigit Thunderbolt Station 3 Plus, we've encountered an issue
> when the USB downstream display connection state changes. The
> problematic sequence observed is:
> ```
> igb_io_error_detected
> igb_down
> igb_io_error_detected
> igb_down
> ```
>
> The second igb_down call blocks at napi_synchronize.

=46rom the backtrace in your commit message, I gain the impression you get=
 a hotplug event for removing the ethernet device. From your commit messag=
e I gain the impression you get an AER as well which is handled in igb_io_=
error_detected()/igb_io_resume(). The problem lies IMHO in the interaction=
 of both.


> Simply avoiding redundant igb_down calls makes the Ethernet of the thund=
erbolt dock unusable.

I'm not too sure if the current code is even perfect in your use-case. Wha=
t happens when you get an AER on the ethernet device (without plugging it =
out at the same time)?

Can you try to AER inject a completion timeout into your ethernet device, =
similar how I showed it in my previous message? Just replace the bdf 09:00=
.0 with the bdf of your ethernet device. I expect a kernel crash like we s=
ee that on our embedded system.


> If Intel can identify when an Ethernet device is within a Thunderbolt
> tunnel, the patch can be more specific.

 Stefan