On 8/30/18 7:43 AM, Peter Zijlstra wrote:
> On Thu, Aug 30, 2018 at 04:29:20PM +0200, Peter Zijlstra wrote:
>
>> Also, once it all works, they should look at switching to _relaxed
>> atomics for LL/SC.
> A little something like so.. should save a few smp_mb().
Finally got to this - time for some spring cleaning ;-)
> ---
>
> diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
> index 4e0072730241..714b54c308b0 100644
> --- a/arch/arc/include/asm/atomic.h
> +++ b/arch/arc/include/asm/atomic.h
> @@ -44,7 +44,7 @@ static inline void atomic_##op(int i, atomic_t *v) \
> } \
>
> #define ATOMIC_OP_RETURN(op, c_op, asm_op) \
> -static inline int atomic_##op##_return(int i, atomic_t *v) \
> +static inline int atomic_##op##_return_relaxed(int i, atomic_t *v) \
> { \
This being relaxed, shoudn't it also remove the smp_mb() before the operation and
leave the generic code to add one / more smp_mb() as appropriate for fully
ordered, acquire and release variants ?
> unsigned int val; \
> \
> @@ -69,8 +69,11 @@ static inline int atomic_##op##_return(int i, atomic_t *v) \
> return val; \
> }
>
> +#define atomic_add_return_relaxed atomic_add_return_relaxed
> +#define atomic_sub_return_relaxed atomic_sub_return_relaxed
> +
> #define ATOMIC_FETCH_OP(op, c_op, asm_op) \
> -static inline int atomic_fetch_##op(int i, atomic_t *v) \
> +static inline int atomic_fetch_##op##_relaxed(int i, atomic_t *v) \
> { \
> unsigned int val, orig; \
> \
> @@ -96,6 +99,14 @@ static inline int atomic_fetch_##op(int i, atomic_t *v) \
> return orig; \
> }
>
> +#define atomic_fetch_add_relaxed atomic_fetch_add_relaxed
> +#define atomic_fetch_sub_relaxed atomic_fetch_sub_relaxed
> +
> +#define atomic_fetch_and_relaxed atomic_fetch_and_relaxed
> +#define atomic_fetch_andnot_relaxed atomic_fetch_andnot_relaxed
> +#define atomic_fetch_or_relaxed atomic_fetch_or_relaxed
> +#define atomic_fetch_xor_relaxed atomic_fetch_xor_relaxed
> +
> #else /* !CONFIG_ARC_HAS_LLSC */
>
> #ifndef CONFIG_SMP
> @@ -379,7 +390,7 @@ static inline void atomic64_##op(long long a, atomic64_t *v) \
> } \
>
> #define ATOMIC64_OP_RETURN(op, op1, op2) \
> -static inline long long atomic64_##op##_return(long long a, atomic64_t *v) \
> +static inline long long atomic64_##op##_return_relaxed(long long a, atomic64_t *v) \
> { \
> unsigned long long val; \
> \
> @@ -401,8 +412,11 @@ static inline long long atomic64_##op##_return(long long a, atomic64_t *v) \
> return val; \
> }
>
> +#define atomic64_add_return_relaxed atomic64_add_return_relaxed
> +#define atomic64_sub_return_relaxed atomic64_sub_return_relaxed
> +
> #define ATOMIC64_FETCH_OP(op, op1, op2) \
> -static inline long long atomic64_fetch_##op(long long a, atomic64_t *v) \
> +static inline long long atomic64_fetch_##op##_relaxed(long long a, atomic64_t *v) \
> { \
> unsigned long long val, orig; \
> \
> @@ -424,6 +438,14 @@ static inline long long atomic64_fetch_##op(long long a, atomic64_t *v) \
> return orig; \
> }
>
> +#define atomic64_fetch_add_relaxed atomic64_fetch_add_relaxed
> +#define atomic64_fetch_sub_relaxed atomic64_fetch_sub_relaxed
> +
> +#define atomic64_fetch_and_relaxed atomic64_fetch_and_relaxed
> +#define atomic64_fetch_andnot_relaxed atomic64_fetch_andnot_relaxed
> +#define atomic64_fetch_or_relaxed atomic64_fetch_or_relaxed
> +#define atomic64_fetch_xor_relaxed atomic64_fetch_xor_relaxed
> +
> #define ATOMIC64_OPS(op, op1, op2) \
> ATOMIC64_OP(op, op1, op2) \
> ATOMIC64_OP_RETURN(op, op1, op2) \
> @@ -434,6 +456,12 @@ static inline long long atomic64_fetch_##op(long long a, atomic64_t *v) \
>
> ATOMIC64_OPS(add, add.f, adc)
> ATOMIC64_OPS(sub, sub.f, sbc)
> +
> +#undef ATOMIC64_OPS
> +#define ATOMIC64_OPS(op, op1, op2) \
> + ATOMIC64_OP(op, op1, op2) \
> + ATOMIC64_FETCH_OP(op, op1, op2)
> +
For clarity I split off this hunk into a seperate patch as it elides generation of
unused bitwise ops.
> ATOMIC64_OPS(and, and, and)
> ATOMIC64_OPS(andnot, bic, bic)
> ATOMIC64_OPS(or, or, or)
>
