| Date | Mon, 9 Nov 2015 11:05:03 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2 16/19] ARC: [plat-eznps] Use dedicated cpu_relax() |
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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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