Re: [PATCH] i2c: virtual i2c adapter support.

[Rodolfo Giometti <giometti-AVVDYK/kqiJWk0Htik3J/w@public.gmane.org>]

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On Mon, Jun 23, 2008 at 09:51:48AM +0200, Peter Korsgaard wrote:
> >>>>> "Jean" == Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org> writes:
> 
> Hi,
> 
>  >> Except that core_lock is static in i2c-core.c.
> 
>  Jean> This construct is broken by design. If you don't know if the
>  Jean> mutex is locked, it means that you're not the one holding
>  Jean> it. If you're not the one holding it, you don't know when it
>  Jean> will be released. So it could be released in the middle of
>  Jean> whatever you are doing which requires the lock to be held, and
>  Jean> that's bad.
> 
> Exactly. Either we put it on hold for the core rework or we add a
> i2c_del_virt_adapter_nolock() variant for the mux-on-i2c case.

The problem is that into i2c_del_virt_adapter() we have to call
i2c_del_adapter() and the lock is already holded by i2c_del_driver()
since the mux is an i2c chip itself.

Do you think that the problem can be resolved if we use
mutex_lock_nested(&core_lock, SINGLE_DEPTH_NESTING) into
i2c_del_adapter()?

Thanks for your help,

Rodolfo

-- 

GNU/Linux Solutions                  e-mail: giometti-AVVDYK/kqiJWk0Htik3J/w@public.gmane.org
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UNIX programming                     skype:  rodolfo.giometti

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