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SubjectRe: [Q] Implementation of spin_lock on i386: why "rep;nop" ?
Alan Cox wrote:
> > The "rep;nop" line looks dubious, since the IA-32 programmer's manual from
> > Intel (year 2001) mentions that the behaviour of REP is undefined when it
> > is not used with string opcodes. BTW, according to the same manual, REP is
> > supposed to modify ecx, but it looks like is is not the case here... which
> > is fortunate, since ecx is never saved. :-)
> rep nop is a pentium IV operation. Its retroactively after testing defined
> to be portable and ok.

Are we sure that the value of ECX doesn't matter on a 386? Or does it
count down doing nops ECX times on a 386?

-- Jamie
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