Re: [patch] SMP alternatives

[jmerkey@ns1.utah-nac.org]

On Wed, Nov 23, 2005 at 11:03:15AM -0800, Linus Torvalds wrote:
> 
> 
> On Wed, 23 Nov 2005, Jeff V. Merkey wrote:
> >
> > The lock prefix '0F' is used for a lot of opcodes other than "lock". Go check
> > the instruction set reference.
> 
> No it's not.
> 
> 0F is indeed the two-byte prefix. But lock is F0, and it's unique.
> 
> Sometimes Intel re-uses the prefixes for other things eg "rep nop", but I 
> don't think that has ever happened for the lock prefix. 
> 
> Besides, the instructions look very different internally in the CPU after 
> decoding, and anyway you'd not want to ignore the lock prefix _early_ at 
> decode time anyway (many instructions turn into illegal instructions with 
> a lock prefix, as do reg-reg modrm bytes). So you'd dismiss the lock 
> prefix not at a byte level, but at a minimum just after the decode stage.
> 
> 		Linus

I always get numbers and words transposed.  Thanks for the correction. 

J
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