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

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> Do you mean that in this sequence:
> 1: CPU A: mutex_enter(mtx)
> 2: CPU A: x = 1
> 3: CPU A: mutex_exit(mtx)
> 4: CPU B: mutex_enter(mtx)
> 5: CPU B: dostuff(x);

> The value changed in step #2 is only guaranteed to be available on
> CPU B after Step #4 runs?

That's how I read Joerg's mail.  My guess is that mutex_exit initiates
a push to RAM; mutex_enter makes sure any other CPUs' mutex_exits'
pushes to RAM have been noticed.  (Of course, depending on the hardware
design, one or both of them may be no-ops...but depending on them to be
is a recipe for nasty surprises when you try to run on other hardware.)

Welcome to SMP. :-þ

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