Re: spinlocks on powerpc

Tom, thank you for your advise.

On 2012/01/01, at 3:39, Tom Lane wrote:

> What I suggest we should do about this is provide an overridable option
> in pg_config_manual.h, along the lines of
>
>     #if defined(__ppc64__) || defined(__powerpc64__)
>     #define USE_PPC_LWARX_MUTEX_HINT
>     #endif
>
> and then test that symbol in s_lock.h.  This will provide an escape
> hatch for anyone who doesn't want the decision tied to 64-bit-ness,
> while still enabling the option automatically for the majority of
> people who could use it.

Fair enough.
I recreated the patch as you advised.

> BTW, while reading the ISA document I couldn't help noticing that LWARX
> is clearly specified to operate on 4-byte quantities (there's LDARX if
> you want to use 8-byte).  Which seems to mean that this bit in s_lock.h
> just represents bogus waste of space:
>
> #if defined(__ppc64__) || defined(__powerpc64__)
> typedef unsigned long slock_t;
> #else
> typedef unsigned int slock_t;
> #endif
>
> Shouldn't we just make slock_t be "int" for both PPC and PPC64?

I'd like it to be untouched for this TAS_SPIN for powerpc
discussion, since it seems it remainds like this for several
years and maybe it needs some more careful consideration
especially for sign extension…

Regards,
Manabu Ori