Re: [PATCH v3 00/11] Introduce cmpxchg128() -- aka. the demise of cmpxchg_double()

Arnd Bergmann
2023-05-15T09:45:33Z

On Mon, May 15, 2023, at 09:56, Peter Zijlstra wrote:
>
> Since v2:
>
> - reworked this_cpu_cmpxchg() to not implicity do u128 but provide explicit
> this_cpu_cmpxchg128() (arnd)
> - added try_cmpxchg12_local() (per the addition of the try_cmpxchg*_local()
> family of functions)
> - slight cleanup of the SLUB conversion (due to rebase and having to touch it)
> - added a 'cleanup' patch for SLUB, since I was staring at that anyway
>

This is clearly an improvement over the previous state, so I'm
happy with that, and the explicit this_cpu_cmpxchg128() interface
addresses most of my previous concerns.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

The need for runtime feature checking in the callers on x86-64 is still
a bit awkward, but this is no worse than before. I understand that
turning this into a compile-time choice would require first settling
a larger debate about raising the default target for distros beyond
the current CONFIG_GENERIC_CPU.

Arnd