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    SubjectRe: [PATCH v2 16/19] ARC: [plat-eznps] Use dedicated cpu_relax()
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    On Monday 09 November 2015 03:35 PM, Peter Zijlstra wrote:
    > 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.

    We discussed this a while back (why do https:/lkml.org/lkml/<year>/.... links work
    psuedo randomly)

    http://marc.info/?l=linux-kernel&m=140350765530113


    >
    >> #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
    >>
    > _______________________________________________
    > linux-snps-arc mailing list
    > linux-snps-arc@lists.infradead.org
    > http://lists.infradead.org/mailman/listinfo/linux-snps-arc
    >



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