Re: [boost] [thread] Some thoughts about "atomic"

From: Roland Schwarz (roland.schwarz_at_[hidden])
Date: 2006-12-01 12:13:31

Peter Dimov wrote:
> #LoadLoad means that loads 
> that precede the barrier cannot be reordered with loads that follow the 
> barrier.

I.e. a instruction sequence

load(A)
#LoadLoad
load(B)

cannot be executed by the processor
as
load(B)
load(A)

but nothing prevents the processor from executing the sequence
load(A)
#LoadLoad
store(B)

as
store(B)
load(A)

right?

Then
load(A)
load(B)
#LoadLoad | #LoadStore
store(C)

cannot be reordered as
load(B)
store(C)
load(A)

Yes?

But in the acquire/release world
load(A)
load(B).acquire
store(C)

can be reordered as
load(B)
store(C)
load(A)

or I am wrong in this assumption?

If I am not wrong, In which respect is your example then an emulation of 
acquire semantics. If I a wrong, what I am missing?

> The four basic primitives can be combined freely, so for example 
> #LoadLoad | #LoadStore means that preceding loads cannot be reordered with 
> subsequent loads or stores. 

I see, thank you.

Roland