Hi,

> We _could_ nop out the actual conditional on the lock result for a 
> spinlock, and turn
> 
> 	lock ; decb %0
> 	js ...
> 
> into
> 
> 	nop ; decb %0
> 	multi-byte-nop

Throwing another patch into the discussion ;)

Comes from some xen guy.  If I read the thing correctly it builds a elf 
section containing a table with both smp and up versions of the code 
path, then patching in the one needed at runtime.  Allows patching both 
directions (up->smp, smp->up) at runtime, for hotplugging (virtual) 
CPU's.  I'm not a inline asm expert though ...

Comments on that one?

   Gerd