[boost] Re: [shared_ptr] Interlocked* - possible bug?

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-09-24 06:30:49

John Torjo wrote:
> Hi Peter,
>
> I think there is a bug in your Interlocked* implementation of
>  shared_ptr (http://www.pdimov.com/cpp/shared_count_x86_exp2.hpp).
>
> In atomic_read you have:
> inline long atomic_read(long volatile const  & value)
> {
>     return value;
> }
>
> I don't believe this is thread-safe.

(repost)

On x86/IA32, I believe that it's as thread safe as you can get. Note that
all count updates go through Interlocked* calls. On IA32, plain reads can
only return a somewhat "surprising" value when interleaved with plain
writes, and even then, the element of surprise is limited. ;-)