[coreboot] v3 printk on SMP

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Sat Feb 21 23:45:07 CET 2009


On 21.02.2009 21:49, Stefan Reinauer wrote:
> On 21.02.2009 21:39 Uhr, Carl-Daniel Hailfinger wrote:
>   
>> On 21.02.2009 21:31, ron minnich wrote:
>>   
>>     
>>> Also I guess it's time to make printk smp-safe.
>>>   
>>>     
>>>       
>> Cool! The big problem here is that you need locking and for that you
>> need something which is shared between CPUs. IIRC this means storing the
>> lock in CAR is a no-go on some processors.
>>   
>>     
>
> Yes. the locking mechanisms are all there but can not be used. (or they
> were, at some point)
>
> The simplest way would be to use a scratchpad register of the chipset as
> a semaphore. That's rather safe but unless on PCIe it can not be done
> atomic.
>   

What about scratchpad registers in the CPU which are guaranteed to be
cache-coherent across multiple cores and processors?

Regards,
Carl-Daniel

-- 
http://www.hailfinger.org/





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