Re: [PATCH 1/2] perf tools: allow building for ARM

From: David Miller
Date: Fri Dec 11 2009 - 05:38:19 EST


From: Ingo Molnar <mingo@xxxxxxx>
Date: Fri, 11 Dec 2009 11:23:16 +0100

>
> * Jamie Iles <jamie.iles@xxxxxxxxxxxx> wrote:
>
>> +#ifdef __arm__
>> +#include "../../arch/arm/include/asm/unistd.h"
>> +#define rmb() asm volatile("":::"memory")
>> +#define cpu_relax() asm volatile("":::"memory")
>> +#endif
>
> cpu_relax() looks fine, but rmb() seems not to match the one that can be
> found in arch/arm/:

I think he did it this way so it can compile in the meantime,
and that doing it right requires runtime cpu detection to
select which barrier instruction is even available on the
current ARM cpu.
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