Subj : Re: What is the real costs of LOCK on x86 multiprocesor machine?
To   : comp.programming.threads
From : Michael Pryhodko
Date : Thu Aug 04 2005 06:52 pm

> "Locked operations are atomic with respect to all other memory operations and all externally
> visible events. Only instruction fetch and page table accesses can pass locked instructions.
> Locked instructions can be used to synchronize data written by one processor and read by
> another processor.
> For the P6 family processors, locked operations serialize all outstanding load and store operations
> (that is, wait for them to complete). This rule is also true for the Pentium 4 and Intel Xeon
> processors, with one exception: load operations that reference weakly ordered memory types
> (such as the WC memory type) may not be serialized."
>
> I'm not sure that last bit means.  Interlocked instructions aren't guaranteed to order
> loads?

Yes loads not serialized in this case, if they reference weakly ordered
memory types -- read about memory types in IA manual.

Bye.
Sincerely yours, Michael.

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