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Date: Sat, 23 Aug 2008 22:39:51 -0600 (MDT)
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To: phk@phk.freebsd.dk
From: "M. Warner Losh" <imp@bsdimp.com>
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Cc: freebsd-usb@freebsd.org
Subject: Re: usb4bsd patch review 
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In message: <10826.1219511738@critter.freebsd.dk>
            "Poul-Henning Kamp" <phk@phk.freebsd.dk> writes:
: In message <20080823.100155.1310242209.imp@bsdimp.com>, "M. Warner Losh" writes
: :
: 
: >While this may be a good idea, I'm hesitant about races that it may
: >introduce.  This is the classic point of attack: do something between
: >steps of a formerly atomic operation that was made non-atomic.  I
: >can't think of anything off the top of my head, but I'm still
: >concerned.
: 
: We have ways of closing the race if need be, but they're all slightly
: kludgy, but I am not overly concerned about those races as long as
: the default is to not give access.

I guess I'm worried about a device that comes and goes and comes back
and there being some difference between the two that causes us to
bogusly do something to the new device that was appropriate for the
old one, but not the new one...

Wraner