Re: [boost] platform specific structures

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-09-20 06:25:46

Matt Hurd wrote:
>> Peter Dimov <pdimov_at_[hidden]> wrote:
>>> Matt Hurd wrote:
>>> I'm interested in getting something like "needs_lock" below into the
>>> normal traits, perhaps as part of boost thread.  It informs you
>>> whether of not an operation on such a contiguous block needs a lock
>>> to be atomic.
>>> 
>>> For example, on ia32 32 bit aligned ops are atomic, on ia64 it is 64
>>> bit.  doubles on ia32 need locking to be atomic, on ia64 they don't.
>> 
>> What do you mean by "atomic"? Do you expect the change to the value
>> to be visible to other threads?
> 
> Just memory consistent / atomic.  That is, if you write to memory or
> read from memory all the bits will be guaranteed to make it as an
> indivisible unit.  It doesn't say anything about the timing of the
> visibility or ordering w.r.t. like memory transactions.

How would you use such a thing? :-)