Re: Pentium 4 and 2.4/2.5

[Alan Cox]

> >             asm volatile("rep ; nop");
> > 
> > (there's not much a "rep nop" _can_ do, after all - the most likely CPU
> > extension would be to raise an "Illegal Opcode" fault).
> 
> Just for the curious, this works on Athlons. :)

What state does it leave the condition codes ?  That matters. 

Take for example

if (!oldval)
                asm volatile(
                        "2:"
                        "cmpl $-1, %0;"
                        "rep; nop;"
                        "je 2b;"
                                : :"m" (current->need_resched));
}

When running SMP with poll_idle enabled. I can't see it changing condition
codes on an athlon but..

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