[U-Boot] driver model is not smp safe

[Tom Rini]

On Thu, Jul 30, 2015 at 12:12:03PM +0800, Bin Meng wrote:

> Hi Simon,
> 
> When adding x86 multi-cpu initialization on a board with 4 cores, I found:
> 
> => cpu list
>   0: cpu at 0               Genuine Intel(R) CPU         @ 1.58GHz
>   1: cpu at 1               Genuine Intel(R) CPU         @ 1.58GHz
>   2: cpu at 2               Genuine Intel(R) CPU         @ 1.58GHz
>   2: cpu at 3               Genuine Intel(R) CPU         @ 1.58GHz
> 
> cpu at 2 and cpu at 3 have the same sequence number, which indicates they
> are running parallelly to get the same sequence number. The call chain
> on an ap is: mp_init_cpu() -> device_probe() -> uclass_resolve_seq().
> Apparently ap2 and ap3 are running at the same time to get the same
> number.
> 
> Note so far all x86 boards that we have enabled x86 multi-cpu
> initialization on only have 2 cores, which will not expose such issue
> as there is no parallel execution among aps.

So what exactly are we doing with these additional cores?  My
recollection of what we do on other arches when we even deal with other
cores is that we bring them "up" and then usually put them in a holding
pattern for the real OS to deal with _or_ it's one of those cases where
we have multiple OSes running and we do what we need to load and release
those other OSes.

-- 
Tom
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