Subj : Re: CMPXCHG timing
To   : comp.programming.threads
From : Michael Pryhodko
Date : Fri Apr 01 2005 06:32 am

> The redundant store isn't observable.  cmpxchg is atomic.  If there's
> a problem, it's with your code elsewhere.  I'm not quite sure what
> you are trying to do, so I don't know where to look or what
suggestions
> to make.

Hmmm... try to run this small test app, you'll that:
- cmpxchg (without LOCK prefix) is not atomic (it is impossible to do
read+write operation atomic on x86 without using bus LOCK)
- this stupid redundant store is quite observable, and basically it
prevent my LOCK'less lock from working! It makes 'unlock' operation
impossible to implement

or on other hand I did a VERY stupid mistake...


About what I am trying to do -- see my answer to another posting.

Bye.
Sincerely yours, Michael.

.