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Date:      Sat, 16 Feb 2008 14:31:47 -0800
From:      Marcel Moolenaar <xcllnt@mac.com>
To:        Rafal Jaworowski <raj@semihalf.com>
Cc:        Marcel Moolenaar <marcel@freebsd.org>, Perforce Change Reviews <perforce@freebsd.org>
Subject:   Re: PERFORCE change 135517 for review
Message-ID:  <504560A3-EABB-4896-8B3E-C7FC89F31EFB@mac.com>
In-Reply-To: <47B75EB3.2020001@semihalf.com>
References:  <200802162141.m1GLfgkj048217@repoman.freebsd.org> <47B75EB3.2020001@semihalf.com>

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On Feb 16, 2008, at 2:07 PM, Rafal Jaworowski wrote:

> Marcel Moolenaar wrote:
>> http://perforce.freebsd.org/chv.cgi?CH=135517
>>
>> Change 135517 by marcel@marcel_jnpr on 2008/02/16 21:41:02
>>
>> 	Save U-Boot's registers at startup and restore them when
>> 	performing a syscall. This way we don't have to compile
>> 	code specially to avoid using those registers. Otherwise
>> 	we have to encode knowledge of those registers in at least
>> 	4 makefiles and introduce a build knob to enable it all.
>> 	This does not allow us to build everything with a single
>> 	build world.
>>
>
> Hi Marcel,
>
> I'm not quite sure this is sufficient... I already had a similar  
> save/restore
> in place, but there is some general problem with U-Boot that leads  
> to hangs
> (experienced):

Interesting, I didn't see any such problems with 1.3.2-rc1.

> - U-Boot does not handle interrupts so there's no context save/ 
> restore of
> exceptions, other than very few cases
>
> - there's one paricular asynchronous way for U-Boot code to regain  
> control
> without those dedicated r14/29 regs saved: decrementer, which can  
> hit anytime
> while in the app code, and which usually leads to hangs/corruption  
> as U-Boot
> code use them blindly

It's really best if U-Boot deals with that.

> PS. I guess it would be good to synchronise somehow the work, as we  
> seem to
> tackle the same pieces, which is a waste of resources.

Yes, definitely...

-- 
Marcel Moolenaar
xcllnt@mac.com





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