CPU A CPU B | CPU A CPU B | cpu A cpu B
----- ----- | ----- ----- | ----- -----
change pte | |
| |
read pte |read pte |read pte
insert TLB | change pte |insert
re-read |insert |re-read
|re-read | change pte
|ptc.l
These scenarii assume that the sequence: insert TLB ;; re-read is executed in the same order for everyone as it is coded. I think a ";;" not sufficient to make sure that the external visibility of the "itc" to generated purges is established first for everyone, before the "re-read" becomes visible.
The manual states that serialization is only necessary before a data access uses the mapping.
It also states on page 3:127:"The visibility of the itc instruction to generated purges (ptc.g, ptc.ga) must occur before subsequent memory operations. From a software perspective, this is similar to acquire semantics. Serialization is still required to observe the side-effects of the translation being present."
We do not use the mapping in the function we are discussing
Agreed.
and I would think that the rfi is certainly serialization enough.
... for the future user mode accesses. I consider an "itc" as completed when: 1. The new (local) translation is available for any new load / store request 2. There is no chance any more to miss an external purge request I think we can agree on the 1st point. As far as the 2nd one is concerned: In order not to break our synchronization algorithm, we need here to make sure that the external visibility of the "itc" to generated purges is established first for everyone, before the "re-read" becomes visible. The only instruction I know of to synchronize with the "itc" mechanism is the "srlz" instruction. Thanks, Zoltan - : send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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