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From: Brian Barrett (bbarrett_at_[hidden])
Date: 2007-07-14 13:06:37


On Jul 14, 2007, at 10:53 AM, Dirk Eddelbuettel wrote:

> Methinks we need to fill in a few blanks here, or make do with non-asm
> solutions. I don't know the problem space that well (being a
> maintainer
> rather than upstream developer) and am looking for guidance.

Either way is an option. There are really only a couple of functions
that have to be implemented:

   * atomic word-size compare and swap
   * memory barrier

We'll emulte atomic adds and spin-locks with compare and swap if not
directly implemented. The memory barrier functions have to exist,
even if they don't do anything. We require compare-and-swap for a
couple of pieces of code, which is why we lost our Sparc v8 support a
couple of releases ago.

> For what it's worth, lam (7.1.2, currently) us available on all build
> architectures for Debian, but it may not push the (hardware)
> envelope as
> hard.

Correct, LAM only had very limited ASM requirements (basically,
memory barrier on platforms that required it -- like PowerPC).

Brian