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From: Hans Petter Selasky <hselasky@freebsd.org>
To: Alexander Leidinger <Alexander@leidinger.net>
Date: Fri, 11 Jul 2008 08:59:52 +0200
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Cc: Perforce Change Reviews <perforce@freebsd.org>, ariff@freebsd.org
Subject: Re: PERFORCE change 144991 for review
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On Friday 11 July 2008, Alexander Leidinger wrote:
> Quoting Hans Petter Selasky <hselasky@FreeBSD.org> (from Thu, 10 Jul
>
> 2008 07:57:37 GMT):
> > http://perforce.freebsd.org/chv.cgi?CH=144991
> >
> > Change 144991 by hselasky@hselasky_laptop001 on 2008/07/10 07:56:37
> >
> >
> > 	These patches into the USB sound system are needed to make
> > 	the Giant-free USB audio driver work seamlessly.
>
> If the mixer uninit can sleep, there's the possibility for a race,
> isn't it? How do you make sure there's no race after not locking the
> mixer?
>
> What about a different approach:
>   - keep the generic sound code as it is (locking of the mixer)
>   - add some uninit flag to the mixer private data
>   - check the flag
>     + if it is not set on uninit, set it
>     + if it is set on uninit (and maybe other mixer operations), abort
>   - unlock the mutex in the uninit
>   - do what can sleep
>   - lock the mutex
>   - return
>
> Bye,
> Alexander.

Detach and uninit routines should always be allowed to sleep in my opinion. 
Ariff: Is there any reason for keeping the mixer lock locked accross the 
UNINIT routine? I think this was done unintentionally.

--HPS