On Tue, Dec 07, 2021 at 05:52:13PM +0100, Peter Zijlstra wrote:
> It's a bit gross, and there seems to be a problem with macro expansion
> of __ofl, but it 'works'.
>
> ---
> diff --git a/arch/x86/include/asm/atomic.h b/arch/x86/include/asm/atomic.h
> index 5e754e895767..921ecfd5a40b 100644
> --- a/arch/x86/include/asm/atomic.h
> +++ b/arch/x86/include/asm/atomic.h
> @@ -263,6 +263,22 @@ static __always_inline int arch_atomic_fetch_xor(int i, atomic_t *v)
> }
> #define arch_atomic_fetch_xor arch_atomic_fetch_xor
>
> +#define atomic_dec_and_test_ofl(_v, __ofl) \
> +({ \
> + __label__ __zero; \
> + __label__ __out; \
> + bool __ret = false; \
> + asm_volatile_goto (LOCK_PREFIX "decl %[var]\n\t" \
> + "jz %l[__zero]\n\t" \
> + "jl %l[__ofl]" \
%l2
and it works much better...
> + : : [var] "m" ((_v)->counter) \
> + : "memory" \
> + : __zero, __ofl); \
> + goto __out; \
> +__zero: __ret = true; \
> +__out: __ret; \
> +})
