linux-kernel - Re: [PATCHv2 04/16] atomics/treewide: make atomic_fetch_add

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Date:   Mon, 04 Jun 2018 16:24:47 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     mark.rutland@....com
CC:     linux-kernel@...r.kernel.org, mark.rutland@....com,
        boqun.feng@...il.com, Will Deacon <will.deacon@....com>,
        vgupta@...opsys.com
Subject:     Re: [PATCHv2 04/16] atomics/treewide: make atomic_fetch_add_unless() optional

On Tue, 29 May 2018 08:43:34 PDT (-0700), mark.rutland@....com wrote:
> Several architectures these have a near-identical implementation based
> on atomic_read() and atomic_cmpxchg() that we can instead define in
> <linux/atomic.h>, so let's do so, using something close to the existing
> x86 implementation with try_cmpxchg().
>
> Where an architecture provides its own atomic_fetch_add_unless(), it
> must define a preprocessor symbol for it. The instrumented atomics are
> updated accordingly.
>
> Note that arch/arc's existing atomic_fetch_add_unless() had redundant
> barriers, as these are already present in its atomic_cmpxchg()
> implementation.
>
> There should be no functional change as a result of this patch.
>
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Acked-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Vineet Gupta <vgupta@...opsys.com>
> ---
>  arch/alpha/include/asm/atomic.h           |  2 +-
>  arch/arc/include/asm/atomic.h             | 28 ----------------------------
>  arch/arm/include/asm/atomic.h             | 11 +----------
>  arch/arm64/include/asm/atomic.h           |  1 -
>  arch/h8300/include/asm/atomic.h           |  1 +
>  arch/hexagon/include/asm/atomic.h         |  1 +
>  arch/ia64/include/asm/atomic.h            | 16 ----------------
>  arch/m68k/include/asm/atomic.h            | 15 ---------------
>  arch/mips/include/asm/atomic.h            | 24 ------------------------
>  arch/parisc/include/asm/atomic.h          | 24 ------------------------
>  arch/powerpc/include/asm/atomic.h         |  1 +
>  arch/riscv/include/asm/atomic.h           |  1 +
>  arch/s390/include/asm/atomic.h            | 15 ---------------
>  arch/sh/include/asm/atomic.h              | 25 -------------------------
>  arch/sparc/include/asm/atomic_32.h        |  2 ++
>  arch/sparc/include/asm/atomic_64.h        | 15 ---------------
>  arch/x86/include/asm/atomic.h             | 21 ---------------------
>  arch/xtensa/include/asm/atomic.h          | 24 ------------------------
>  include/asm-generic/atomic-instrumented.h |  4 +++-
>  include/asm-generic/atomic.h              | 11 -----------
>  include/linux/atomic.h                    | 23 +++++++++++++++++++++++
>  21 files changed, 34 insertions(+), 231 deletions(-)
> [...]
> diff --git a/arch/riscv/include/asm/atomic.h b/arch/riscv/include/asm/atomic.h
> index 18259e90f57e..5f161daefcd2 100644
> --- a/arch/riscv/include/asm/atomic.h
> +++ b/arch/riscv/include/asm/atomic.h
> @@ -349,6 +349,7 @@ static __always_inline int atomic_fetch_add_unless(atomic_t *v, int a, int u)
>  		: "memory");
>  	return prev;
>  }
> +#define atomic_fetch_add_unless atomic_fetch_add_unless
>
>  #ifndef CONFIG_GENERIC_ATOMIC64
>  static __always_inline long __atomic64_add_unless(atomic64_t *v, long a, long u)

Acked-by: Palmer Dabbelt <palmer@...ive.com>

Thanks!