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From: Oliver Neukum <oliver@neukum.org>
To: Duncan Sands <baldrick@free.fr>, Alan Stern <stern@rowland.harvard.edu>
Subject: Re: [linux-usb-devel] Re: [OOPS,  usbcore, releaseintf] 2.6.0-test10-mm1
Date: Wed, 10 Dec 2003 17:58:02 +0100
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Cc: David Brownell <david-b@pacbell.net>, Vince <fuzzy77@free.fr>,
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References: <Pine.LNX.4.44L0.0312081754480.2034-100000@ida.rowland.org> <200312101720.22731.oliver@neukum.org> <200312101749.17173.baldrick@free.fr>
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Am Mittwoch, 10. Dezember 2003 17:49 schrieb Duncan Sands:
> On Wednesday 10 December 2003 17:20, Oliver Neukum wrote:
> > Am Mittwoch, 10. Dezember 2003 14:22 schrieb Duncan Sands:
> > > > That leads to the question of how to assure that the device doesn't go
> > > > away before usb_set_configuration is called.  Perhaps
> > > > usb_set_configuration and usb_unbind_interface should be changed to
> > > > require the caller to hold the serialize lock.
> > >
> > > How about
> > >
> > > __usb_set_configuration - lockless version
> > > usb_set_configuration - locked version
> >
> > Partially done.
> > That's what the _physical version of usb_reset_device() is about.
> 
> Unfortunately, usb_physical_reset_device calls usb_set_configuration
> which takes dev->serialize.

That is bad, but the solution is obvious.
All such operations need a _physical version.
At first sight this may look less elegant than some lock dropping schemes,
but it is a solution that produces obviously correct code paths with respect
to locking.

	Regards
		Oliver