Subj : Re: A question about atomic_ptr
To   : comp.programming.threads
From : Peter Dimov
Date : Fri Apr 15 2005 01:37 pm

Chris Thomasson wrote:
>> The point is that you no longer need tricks in the copy constructor.
>> The original race is only a problem when the count is 1 so that you
>> can have the
>> assignment destroy the count and then the copy constructor attempt to
>> increment it.
>
> No.

Yes, it's broken. A non-tricky copy constructor cannot be made 
race-resistant, no matter how I fiddle with the assignment. Its thread can 
always be preempted after it loads the pointer for just enough time for some 
other thread to destroy the count.

.