On 4/8/25 10:22, Jason Gunthorpe wrote:
> The core atomic code has a number of macros where it elaborates
> architecture primitives into more functions. ARC uses
> arch_atomic64_cmpxchg() as it's architecture primitive which disable alot
> of the additional functions.
>
> Instead provide arch_cmpxchg64_relaxed() as the primitive and rely on the
> core macros to create arch_cmpxchg64().
>
> The macros will also provide other functions, for instance,
> try_cmpxchg64_release(), giving a more complete implementation.
>
> Suggested-by: Mark Rutland <mark.rutl...@arm.com>
> Link: https://lore.kernel.org/r/Z0747n5bSep4_1VX@J2N7QTR9R3
> Signed-off-by: Jason Gunthorpe <j...@nvidia.com>
Acked-by: Vineet Gupta <vgu...@kernel.org>
> ---
> arch/arc/include/asm/atomic64-arcv2.h | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arc/include/asm/atomic64-arcv2.h
> b/arch/arc/include/asm/atomic64-arcv2.h
> index 9b5791b8547133..73080a664369b4 100644
> --- a/arch/arc/include/asm/atomic64-arcv2.h
> +++ b/arch/arc/include/asm/atomic64-arcv2.h
> @@ -137,12 +137,9 @@ ATOMIC64_OPS(xor, xor, xor)
> #undef ATOMIC64_OP_RETURN
> #undef ATOMIC64_OP
>
> -static inline s64
> -arch_atomic64_cmpxchg(atomic64_t *ptr, s64 expected, s64 new)
> +static inline u64 __arch_cmpxchg64_relaxed(volatile void *ptr, u64 old, u64
> new)
> {
> - s64 prev;
> -
> - smp_mb();
> + u64 prev;
>
> __asm__ __volatile__(
> "1: llockd %0, [%1] \n"
> @@ -152,14 +149,12 @@ arch_atomic64_cmpxchg(atomic64_t *ptr, s64 expected,
> s64 new)
> " bnz 1b \n"
> "2: \n"
> : "=&r"(prev)
> - : "r"(ptr), "ir"(expected), "r"(new)
> - : "cc"); /* memory clobber comes from smp_mb() */
> -
> - smp_mb();
> + : "r"(ptr), "ir"(old), "r"(new)
> + : "memory", "cc");
>
> return prev;
> }
> -#define arch_atomic64_cmpxchg arch_atomic64_cmpxchg
> +#define arch_cmpxchg64_relaxed __arch_cmpxchg64_relaxed
>
> static inline s64 arch_atomic64_xchg(atomic64_t *ptr, s64 new)
> {
>
> base-commit: ea8f6ee2111cd78b32d0363ea630ba9b08ada22d
Thx for this.
FWIW I missed the cmpxchg API when the rest of atomics were relaxed in commit
301014cf6d728 ("ARC: atomic_cmpxchg/atomic_xchg: implement relaxed variants")
Added to ARC for-curr (for next)
Thx,
-Vineet
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