Re: Test atomic operations on SPARC 32-bit
Hi Adrian,
> On 12/09/2017 12:21 AM, Petr Vorel wrote:
> >> I'm asking because atomic operations were only added with SPARCv8+ and later.
> > SPARCv8 would be enough as SPARCv7 is dead. So still no hw support.
> From what I have heard, SPARCv7 should actually work since people added
> kernel helpers to the Linux kernel to emulate the atomics for v7 hardware.
Oh yes, I've heard that as well. I'm looking into kernel source
arch/sparc/lib/atomic32.c
arch/sparc/include/asm/atomic_32.h
According to the sources they implemented it by hashing the object address and indexing
into an array of spinlocks.
Also LWN is talking about it
https://lwn.net/Articles/695257/
> SPARCv8 doesn't have Compare-And-Swap either, SPARCv8+ does which is what
> most people run these days when they run 32-Bit-SPARC.
> >> In any case, the Gentoo people are still on 32-Bit SPARC. You might ask there
> >> first (see #gentoo-sparc on Freenode). Otherwise, we will have to create a
> >> 32-Bit chroot for you but that would probably take a bit longer.
> > OK, I'll ask them and if not works I'll come back.
> They just started working on their SPARC port again.
Good to know, thanks!
> Adrian
Kind regards,
Petr
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