Re: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race withpreemptible kernel and CPU hotplug

[Mathieu Desnoyers]

* H. Peter Anvin (hpa@xxxxxxxxx) wrote:
> 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

So should I wait a bit for more comments or straightforwardly submit
this as a patch rather than RFC ?

Mathieu



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Mathieu Desnoyers
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