From owner-freebsd-wireless@freebsd.org  Mon Sep  5 08:41:33 2016
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Subject: Re: Deadlock between device_detach() and usbd_do_request_flags()
To: Andriy Voskoboinyk <avos@freebsd.org>, Adrian Chadd <adrian@freebsd.org>
References: <op.ynaawb2n4dikkl@localhost>
 <4cf378ff-63e1-7cdc-6120-9578fceec20d@selasky.org>
Cc: "freebsd-wireless@freebsd.org" <freebsd-wireless@freebsd.org>,
 "freebsd-usb@freebsd.org" <freebsd-usb@freebsd.org>
From: Hans Petter Selasky <hps@selasky.org>
Message-ID: <55cff8ce-6132-53ec-3419-d27286dce622@selasky.org>
Date: Mon, 5 Sep 2016 10:46:12 +0200
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On 09/05/16 09:53, Hans Petter Selasky wrote:
>
> Hi,
>
> I think the right solution is to let usbd_do_request_flags() use its own
> SX lock for synchronization, instead of re-using the enumeration SX
> lock. What do you think about that?
>
> --HPS
>

Hi,

Another approach which will work is to setup your own USB control 
endpoint xfer, and use that. I'll have a look and see what can be done.

--HPS