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SubjectRe: [PATCH v2 16/19] ARC: [plat-eznps] Use dedicated cpu_relax()
On Sat, Nov 07, 2015 at 12:52:34PM +0200, Noam Camus wrote:
> diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
> index 7266ede..50f9bae 100644
> --- a/arch/arc/include/asm/processor.h
> +++ b/arch/arc/include/asm/processor.h
> @@ -58,12 +58,21 @@ struct task_struct;
> * get optimised away by gcc
> */
> #ifdef CONFIG_SMP
> +#ifndef CONFIG_EZNPS_MTM_EXT
> #define cpu_relax() __asm__ __volatile__ ("" : : : "memory")
> #else
> +#define cpu_relax() \
> + __asm__ __volatile__ (".word %0" : : "i"(CTOP_INST_SCHD_RW) : "memory")
> +#endif
> +#else
> #define cpu_relax() do { } while (0)

I'm fairly sure this is incorrect. Even on UP we expect cpu_relax() to
be a compiler barrier.

> #endif
>
> +#ifndef CONFIG_EZNPS_MTM_EXT
> #define cpu_relax_lowlatency() cpu_relax()
> +#else
> +#define cpu_relax_lowlatency() barrier()
> +#endif

At which point you can unconditionally use that definition.

>
> #define copy_segments(tsk, mm) do { } while (0)
> #define release_segments(mm) do { } while (0)
> --
> 1.7.1
>


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