Re: better atomics - v0.6

On 2014-09-24 00:27:25 +0300, Oskari Saarenmaa wrote:
> 23.09.2014, 15:18, Andres Freund kirjoitti:
> >On 2014-09-23 13:50:28 +0300, Oskari Saarenmaa wrote:
> >>23.09.2014, 00:01, Andres Freund kirjoitti:
> >>>The patches:
> >>>0001: The actual atomics API
> >>
> >>I tried building PG on Solaris 10/Sparc using GCC 4.9.0 (buildfarm animal
> >>dingo) with this patch but regression tests failed due to:
> >
> >Btw, if you could try sun studio it'd be great. I wrote the support for
> >it blindly, and I'd be surprised if I got it right on the first try.
> 
> I just installed Solaris Studio 12.3 and tried compiling this:

Cool.

> "../../../../src/include/port/atomics/generic-sunpro.h", line 54: return
> value type mismatch
> "../../../../src/include/port/atomics/generic-sunpro.h", line 77: return
> value type mismatch
> "../../../../src/include/port/atomics/generic-sunpro.h", line 79: #if-less
> #endif
> "../../../../src/include/port/atomics/generic-sunpro.h", line 81: #if-less
> #endif
> 
> atomic_add_64 and atomic_add_32 don't return anything (the atomic_add_*_nv
> variants return the new value) and there were a few extra #endifs.
> Regression tests pass after applying the attached patch which defines
> PG_HAS_ATOMIC_ADD_FETCH_U32.

Thanks for the fixes!

Hm. I think then it's better to simply not implement addition and rely
on cmpxchg.

> Also, it's not possible to compile PG with FORCE_ATOMICS_BASED_SPINLOCKS
> with these patches:
> 
> "../../../../src/include/storage/s_lock.h", line 868: #error: PostgreSQL
> does not have native spinlock support on this platform....
> 
> atomics/generic.h would implement atomic flags using operations exposed by
> atomics/generic-sunpro.h, but atomics/fallback.h is included before it and
> it defines functions for flag operations which s_lock.h doesn't want to use.

Right. It should check not just for flag support, but also for 32bit
atomics. Easily fixable.

I'll send a new version with your fixes incorporated tomorrow.

Thanks for looking into this! Very helpful.

Greetings,

Andres Freund

-- 
 Andres Freund	                   http://www.2ndQuadrant.com/
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