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Re: 4.x -> 5.x locking?

>> Does mutex_exit also implicitly push writes to main RAM, or whatever
>> else is necessary to make them visible to other CPUs?
> I don't think it guarantees it by itself.  That is, if you want to
> access the data on a different CPU, you either need to take the mutex
> (and the read barrier in mutex_enter) or issue an explicit barrier.

Yes, I got slightly careless.  I should have said, mutex_exit on the
writing CPU plus mutex_enter on the reading CPU.

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