Re: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptiblekernel and CPU hotplug

[H. Peter Anvin]

Jeremy Fitzhardinge wrote:
> Ah, OK.  I'd thought we started unlocked, but given that I've just been 
> disassembling the kernel and looking at the lock prefixes, that's a bit 
> of a braino on my part.
>
> BTW, using the ds prefix allows us to undo the hack of dealing with 
> locked instructions with exception handlers.  There was a bug where if 
> we do lock->nop, then the address of a faulting instruction changes, so 
> we need exception records for both the locked and unlocked forms.  Using 
> ds means the instruction size doesn't change, so we only need one 
> exception record.  I don't remember off hand where that happens.

Using %ds: rather than nop really seems to solve a whole lot of 
problems, and might even be faster to boot.  It really sounds like a 
no-brainer.

	-hpa
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