Are indivisible operations still indivisible on multiprocessor and multicore systems?
- by Steve314
As per the title, plus what are the limitations and gotchas.
For example, on x86 processors, alignment for most data types is optional - an optimisation rather than a requirement. That means that a pointer may be stored at an unaligned address, which in turn means that pointer might be split over a cache page boundary.
Obviously this could be done if you work hard enough on any processor (picking out particular bytes etc), but not in a way where you'd still expect the write operation to be indivisible.
I seriously doubt that a multicore processor can ensure that other cores can guarantee a consistent all-before or all-after view of a written pointer in this unaligned-write-crossing-a-page-boundary situation.
Am I right? And are there any similar gotchas I haven't thought of?
