Re: Spinlocks and compiler/memory barriers

On 2014-07-01 20:21:37 -0400, Tom Lane wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
> > On 2014-07-01 23:21:07 +0100, Mark Cave-Ayland wrote:
> >> Also if you're struggling for Sun buildfarm animals, recent versions of QEMU
> >> will quite happily install and run later versions of 32-bit Solaris over
> >> serial, and 2.0 even manages to give you a cgthree framebuffer for the full
> >> experience.
>
> > Well. I have to admit I'm really not interested in investing that much
> > time in something I've no stake in. If postgres developers have to put
> > emulated machines to develop features something imo went seriously
> > wrong. That's more effort than at least I'm willing to spend.
>
> Perhaps more to the point, I have no faith at all that an emulator will
> mimic multiprocessor timing behavior to the level of detail needed to
> tell whether memory-barrier-related logic works. See the VAX discussion
> just a couple days ago.

Well, it would allow us to see wether fixed stuff actually compiles and
runs - that's not nothing. The biggest problem with fixing stuff like
armv5, sparc8, whatever is that it requires adding stuff to our inline
assembly. It's easy to accidentally make it not compile, but
comparatively harder to make the behaviour even worse than before.

Greetings,

Andres Freund

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