Messages in this thread | | | Date | Fri, 11 Dec 2009 11:41:26 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 1/2] perf tools: allow building for ARM |
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* David Miller <davem@davemloft.net> wrote:
> From: Ingo Molnar <mingo@elte.hu> > Date: Fri, 11 Dec 2009 11:23:16 +0100 > > > > > * Jamie Iles <jamie.iles@picochip.com> 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.
Yeah. We can merge a quick patch for it if runtime detection is difficult - but if then such a patch should err on the side of using the barrier instruction unconditionally - even if this causes perf to segfault on certain (older? UP configured?) ARM cores.
Ingo
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