On Sun, 27 Nov 2022 19:43:47 -0800, Davidlohr Bueso <dave@xxxxxxxxxxxx> wrote:
> This gets rid of the last references to smp_read_barrier_depends()
> which for the kernel side was removed in v5.9. The serialization
> required for Alpha is done inside READ_ONCE() instead of having
> users deal with it. Simply use a full barrier, the architecture
> does not have rmb in the first place.
>
> Signed-off-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Reviewed-by: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
> ---
> tools/virtio/ringtest/main.h | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/tools/virtio/ringtest/main.h b/tools/virtio/ringtest/main.h
> index 9ed09caa659e..b68920d52750 100644
> --- a/tools/virtio/ringtest/main.h
> +++ b/tools/virtio/ringtest/main.h
> @@ -140,12 +140,6 @@ static inline void busy_wait(void)
> #define smp_wmb() smp_release()
> #endif
>
> -#ifdef __alpha__
> -#define smp_read_barrier_depends() smp_acquire()
> -#else
> -#define smp_read_barrier_depends() do {} while(0)
> -#endif
> -
> static __always_inline
> void __read_once_size(const volatile void *p, void *res, int size)
> {
> @@ -175,13 +169,22 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
> }
> }
>
> +#ifdef __alpha__
> #define READ_ONCE(x) \
> ({ \
> union { typeof(x) __val; char __c[1]; } __u; \
> __read_once_size(&(x), __u.__c, sizeof(x)); \
> - smp_read_barrier_depends(); /* Enforce dependency ordering from x */ \
> + smp_mb(); /* Enforce dependency ordering from x */ \
> __u.__val; \
> })
> +#else
> +#define READ_ONCE(x) \
> +({ \
> + union { typeof(x) __val; char __c[1]; } __u; \
> + __read_once_size(&(x), __u.__c, sizeof(x)); \
> + __u.__val; \
> +})
> +#endif
>
> #define WRITE_ONCE(x, val) \
> ({ \
> --
> 2.38.1
>
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