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From:   Jookia <contact@jookia.org>
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     linux-usb@vger.kernel.org
Subject: Re: acm_port_shutdown hangs for 30 seconds
Message-ID: <YrrILGzC2R3qGiHu@novena-choice-citizen>
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 <YrmpLXcPeHW4fnvz@kroah.com>
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Hi Greg,

Thanks for getting back to this!

On Mon, Jun 27, 2022 at 02:57:17PM +0200, Greg KH wrote:
> What host controller driver is this showing up on?

I have the following modules loaded:

xhci_pci_renesas
xhci_pci
xhci_hcd

This isn't an ARM board or anything, this is a standard x86 desktop
(B450 plus motherboard, Ryzen 3700x chipset)- but I believe I've had the
same error when using serial cables on a years older computer and in
general when doing embedded development.

I believe this issue is related to buggy serial devices, in particular
ones run by a microcontroller like an ATmega32u4 and perhaps Linux USB
gadget where the device is abruptly reset but the serial session isn't
terminated.

The host device USB system has to time out then, which is fine, but in
userspace this seems to hang close() instead of doing this
asynchronously.

> thanks,
> 
> greg k-h

Jookia.