Around Fri 22 Apr 2016 11:04:19 +0200 or thereabout, Peter Zijlstra wrote:
> Implement FETCH-OP atomic primitives, these are very similar to the
> existing OP-RETURN primitives we already have, except they return the
> value of the atomic variable _before_ modification.
>
> This is especially useful for irreversible operations -- such as
> bitops (because it becomes impossible to reconstruct the state prior
> to modification).
>
>
>
> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Looks good.
Acked-by: Hans-Christian Noren Egtvedt <egtv...@samfundet.no>
> ---
> arch/avr32/include/asm/atomic.h | 56
> ++++++++++++++++++++++++++++++++++++----
> 1 file changed, 51 insertions(+), 5 deletions(-)
>
> --- a/arch/avr32/include/asm/atomic.h
> +++ b/arch/avr32/include/asm/atomic.h
> @@ -41,21 +41,51 @@ static inline int __atomic_##op##_return
> return result; \
> }
>
> +#define ATOMIC_FETCH_OP(op, asm_op, asm_con) \
> +static inline int __atomic_fetch_##op(int i, atomic_t *v) \
> +{ \
> + int result, val; \
> + \
> + asm volatile( \
> + "/* atomic_fetch_" #op " */\n" \
> + "1: ssrf 5\n" \
> + " ld.w %0, %3\n" \
> + " mov %1, %0\n" \
> + " " #asm_op " %1, %4\n" \
> + " stcond %2, %1\n" \
> + " brne 1b" \
> + : "=&r" (result), "=&r" (val), "=o" (v->counter) \
> + : "m" (v->counter), #asm_con (i) \
> + : "cc"); \
> + \
> + return result; \
> +}
> +
> ATOMIC_OP_RETURN(sub, sub, rKs21)
> ATOMIC_OP_RETURN(add, add, r)
> +ATOMIC_FETCH_OP (sub, sub, rKs21)
> +ATOMIC_FETCH_OP (add, add, r)
>
> -#define ATOMIC_OP(op, asm_op)
> \
> +#define atomic_fetch_or atomic_fetch_or
> +
> +#define ATOMIC_OPS(op, asm_op)
> \
> ATOMIC_OP_RETURN(op, asm_op, r)
> \
> static inline void atomic_##op(int i, atomic_t *v) \
> { \
> (void)__atomic_##op##_return(i, v); \
> +} \
> +ATOMIC_FETCH_OP(op, asm_op, r)
> \
> +static inline int atomic_fetch_##op(int i, atomic_t *v) \
> +{ \
> + return __atomic_fetch_##op(i, v); \
> }
>
> -ATOMIC_OP(and, and)
> -ATOMIC_OP(or, or)
> -ATOMIC_OP(xor, eor)
> +ATOMIC_OPS(and, and)
> +ATOMIC_OPS(or, or)
> +ATOMIC_OPS(xor, eor)
>
> -#undef ATOMIC_OP
> +#undef ATOMIC_OPS
> +#undef ATOMIC_FETCH_OP
> #undef ATOMIC_OP_RETURN
>
> /*
> @@ -87,6 +117,14 @@ static inline int atomic_add_return(int
> return __atomic_add_return(i, v);
> }
>
> +static inline int atomic_fetch_add(int i, atomic_t *v)
> +{
> + if (IS_21BIT_CONST(i))
> + return __atomic_fetch_sub(-i, v);
> +
> + return __atomic_fetch_add(i, v);
> +}
> +
> /*
> * atomic_sub_return - subtract the atomic variable
> * @i: integer value to subtract
> @@ -102,6 +140,14 @@ static inline int atomic_sub_return(int
> return __atomic_add_return(-i, v);
> }
>
> +static inline int atomic_fetch_sub(int i, atomic_t *v)
> +{
> + if (IS_21BIT_CONST(i))
> + return __atomic_fetch_sub(i, v);
> +
> + return __atomic_fetch_add(-i, v);
> +}
> +
> /*
> * __atomic_add_unless - add unless the number is a given value
> * @v: pointer of type atomic_t
--
mvh
Hans-Christian Noren Egtvedt
