PERFORCE change 135517 for review

[Marcel Moolenaar]

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 at 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 at mac.com