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SubjectRe: TSCs are a no-no on i386
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On Mer, 2003-07-30 at 19:45, Adrian Bunk wrote:
> Note that this can also allow Step-A 486's to correctly run multi-thread
> applications since cmpxchg has a wrong opcode on this early CPU.
>
> Don't use this to enable multi-threading on an SMP machine, the lock
> atomicity can't be guaranted!

That is of course the other problem with this approach - you can't
really get the intended results without some extremely heavyweight code
(using an IPI to halt all CPU's, doing the access and then resuming
them)

The bigger problem (and certainly with some of the cmov emulation hacks
I've seen) is getting the security checking right when you need to
reprocess the user data - another reason to do it in userspace with a
preload 8)

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