Re: [boost] Re: Boost.Threads draft library submission

From: Beman Dawes (bdawes_at_[hidden])
Date: 2001-03-15 19:24:29

At 04:28 PM 3/15/2001, williamkempf_at_[hidden] wrote:

 >> Am I missing something?
 >
 >Just a small detail.  A classic example is the "Double-Checked
 >Locking Optimization" pattern.  On MP (multiple processor) machines
 >the machines architecture does some optimizations that can result in
 >this pattern not working.  In addition to language constructs such as
 >volatile you need to use a platform specific "memory barrier" to
 >insure the CPU(s) don't optimize the code in such a way as to cause
 >incorrect behavior in this pattern.  The atomic_t type built on using
 >a mutex may be subject to this same error (this goes beyond my
 >expertise on the subject).  There was a recent thread on this subject
 >on the Usenet.

So if I understand you correctly, on some platforms the hoops you have to 
jump through are multi-step sequences of platform specific features.  Very 
tricky, but doesn't the logic still hold?  You can make it work as long as 
you follow the platform's rules.

 >The point is, however, these issues can all be addressed in a
 >platform specific manner with out the need for a change to the
 >interface of atomic_t.

Yes, understood.

Just out of curiosity, what platforms are we talking about?  Are they 
exotic ones where users expect to have to do a lot of hand tailoring?

--Beman