linux-kernel - Re: [PATCH v9 1/2] arch/*: Add CONFIG_ARCH_HAVE

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Date:   Tue, 15 May 2018 12:54:01 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Bart Van Assche <bart.vanassche@....com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        Bart Van Assche <bart.vanassche@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        Helge Deller <deller@....de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        "David S . Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v9 1/2] arch/*: Add CONFIG_ARCH_HAVE_CMPXCHG64

Hi Bart,

Bart Van Assche <bart.vanassche@....com> writes:
>
...
> diff --git a/Documentation/features/locking/cmpxchg64/arch-support.txt b/Documentation/features/locking/cmpxchg64/arch-support.txt
> new file mode 100644
> index 000000000000..65b3290ce5d5
> --- /dev/null
> +++ b/Documentation/features/locking/cmpxchg64/arch-support.txt
> @@ -0,0 +1,31 @@
> +#
> +# Feature name:          cmpxchg64
> +#         Kconfig:       ARCH_HAVE_CMPXCHG64
> +#         description:   arch supports the cmpxchg64() API
> +#
> +    -----------------------
> +    |         arch |status|
> +    -----------------------
> +    |       alpha: |  ok  |
> +    |         arc: | TODO |
> +    |         arm: |!thumb|
> +    |       arm64: |  ok  |
> +    |         c6x: | TODO |
> +    |       h8300: | TODO |
> +    |     hexagon: | TODO |
> +    |        ia64: |  ok  |
> +    |        m68k: |  ok  |
> +    |  microblaze: | TODO |
> +    |        mips: |64-bit|
> +    |       nios2: | TODO |
> +    |    openrisc: | TODO |
> +    |      parisc: |  ok  |
> +    |     powerpc: |64-bit|

I think that is correct for powerpc, we don't have a 32-bit
implementation and there's no fallback it seems.

> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -150,6 +150,7 @@ config PPC
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
>  	select ARCH_HAS_ZONE_DEVICE		if PPC_BOOK3S_64
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
> +	select ARCH_HAVE_CMPXCHG64

So shouldn't this should be:

+	select ARCH_HAVE_CMPXCHG64		if PPC64

And it should be sorted alphabetically, ie. above the previous NMI entry.

cheers