Re: [Q] Implementation of spin_lock on i386: why "rep;nop" ?

[Alan Cox]

> 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. 

Alan