linux-kernel - Re: [PATCH v2 1/5] hash.h: remove unused define directive

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Date:   Sat, 2 Oct 2021 15:19:56 +0800
From:   David Gow <davidgow@...gle.com>
To:     Isabella Basso <isabellabdoamaral@....br>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>, ferreiraenzoa@...il.com,
        augusto.duraes33@...il.com,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Daniel Latypov <dlatypov@...gle.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        ~lkcamp/patches@...ts.sr.ht, rodrigosiqueiramelo@...il.com
Subject: Re: [PATCH v2 1/5] hash.h: remove unused define directive

On Mon, Sep 27, 2021 at 6:33 AM Isabella Basso <isabellabdoamaral@....br> wrote:
>
> Currently, there exist hash_32() and __hash_32() functions, which were
> introduced in a patch [1] targeting architecture specific optimizations.
> These functions can be overridden on a per-architecture basis to achieve
> such optimizations. They must set their corresponding define directive
> (HAVE_ARCH_HASH_32 and HAVE_ARCH__HASH_32, respectively) so that header
> files can deal with these overrides properly.
>
> As the supported 32-bit architectures that have their own hash function
> implementation (i.e. m68k, Microblaze, H8/300, pa-risc) have only been
> making use of the (more general) __hash_32() function (which only lacks
> a right shift operation when compared to the hash_32() function),
> remove the define directive corresponding to the arch-specific hash_32()
> implementation.
>
> [1] https://lore.kernel.org/lkml/20160525073311.5600.qmail@ns.sciencehorizons.net/
>
> Changes since v1:
> - As suggested by David Gow:
>   1. Reword commit message.

Maybe move this changelog to below the "---", so it doesn't show up in
the final commit message?

>
> Tested-by: David Gow <davidgow@...gle.com>
> Co-developed-by: Augusto Durães Camargo <augusto.duraes33@...il.com>
> Signed-off-by: Augusto Durães Camargo <augusto.duraes33@...il.com>
> Co-developed-by: Enzo Ferreira <ferreiraenzoa@...il.com>
> Signed-off-by: Enzo Ferreira <ferreiraenzoa@...il.com>
> Signed-off-by: Isabella Basso <isabellabdoamaral@....br>
> ---

This looks sensible enough to me. Since no-one seems to be speaking up
in architecture-specific hash_32()'s defence, let's get rid of it.

Reviewed-by: David Gow <davidgow@...gle.com>

Cheers,
-- David


>  include/linux/hash.h       |  5 +----
>  lib/test_hash.c            | 24 +-----------------------
>  tools/include/linux/hash.h |  5 +----
>  3 files changed, 3 insertions(+), 31 deletions(-)
>
> diff --git a/include/linux/hash.h b/include/linux/hash.h
> index ad6fa21d977b..38edaa08f862 100644
> --- a/include/linux/hash.h
> +++ b/include/linux/hash.h
> @@ -62,10 +62,7 @@ static inline u32 __hash_32_generic(u32 val)
>         return val * GOLDEN_RATIO_32;
>  }
>
> -#ifndef HAVE_ARCH_HASH_32
> -#define hash_32 hash_32_generic
> -#endif
> -static inline u32 hash_32_generic(u32 val, unsigned int bits)
> +static inline u32 hash_32(u32 val, unsigned int bits)
>  {
>         /* High bits are more random, so use them. */
>         return __hash_32(val) >> (32 - bits);
> diff --git a/lib/test_hash.c b/lib/test_hash.c
> index 0ee40b4a56dd..d4b0cfdb0377 100644
> --- a/lib/test_hash.c
> +++ b/lib/test_hash.c
> @@ -94,22 +94,7 @@ test_int_hash(unsigned long long h64, u32 hash_or[2][33])
>                         pr_err("hash_32(%#x, %d) = %#x > %#x", h0, k, h1, m);
>                         return false;
>                 }
> -#ifdef HAVE_ARCH_HASH_32
> -               h2 = hash_32_generic(h0, k);
> -#if HAVE_ARCH_HASH_32 == 1
> -               if (h1 != h2) {
> -                       pr_err("hash_32(%#x, %d) = %#x != hash_32_generic() "
> -                               " = %#x", h0, k, h1, h2);
> -                       return false;
> -               }
> -#else
> -               if (h2 > m) {
> -                       pr_err("hash_32_generic(%#x, %d) = %#x > %#x",
> -                               h0, k, h1, m);
> -                       return false;
> -               }
> -#endif
> -#endif
> +
>                 /* Test hash_64 */
>                 hash_or[1][k] |= h1 = hash_64(h64, k);
>                 if (h1 > m) {
> @@ -227,13 +212,6 @@ test_hash_init(void)
>  #else
>         pr_info("__hash_32() has no arch implementation to test.");
>  #endif
> -#ifdef HAVE_ARCH_HASH_32
> -#if HAVE_ARCH_HASH_32 != 1
> -       pr_info("hash_32() is arch-specific; not compared to generic.");
> -#endif
> -#else
> -       pr_info("hash_32() has no arch implementation to test.");
> -#endif
>  #ifdef HAVE_ARCH_HASH_64
>  #if HAVE_ARCH_HASH_64 != 1
>         pr_info("hash_64() is arch-specific; not compared to generic.");
> diff --git a/tools/include/linux/hash.h b/tools/include/linux/hash.h
> index ad6fa21d977b..38edaa08f862 100644
> --- a/tools/include/linux/hash.h
> +++ b/tools/include/linux/hash.h
> @@ -62,10 +62,7 @@ static inline u32 __hash_32_generic(u32 val)
>         return val * GOLDEN_RATIO_32;
>  }
>
> -#ifndef HAVE_ARCH_HASH_32
> -#define hash_32 hash_32_generic
> -#endif
> -static inline u32 hash_32_generic(u32 val, unsigned int bits)
> +static inline u32 hash_32(u32 val, unsigned int bits)
>  {
>         /* High bits are more random, so use them. */
>         return __hash_32(val) >> (32 - bits);
> --
> 2.33.0
>