Re: [boost] Lock-free atomic_shared_ptr<T>?

From: Peter Dimov (pdimov_at_[hidden])
Date: 2008-01-18 13:34:11

Jeffrey Yasskin:

> Porting lock-free data structures from Java is complicated by the fact
> that the implementations assume garbage collection. There are a few
> techniques available for dealing with manual memory management without
> locks, but they complicate the implementation of algorithms that are
> complex enough already. So I'm thinking about trying to implement an
> atomic_shared_ptr<T> along the lines of the interface for other
> atomics defined in
> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2427.html but
> using shared_ptr<T> as a value type. The implementation I'm thinking
> of uses hazard pointers
> (http://erdani.org/publications/cuj-2004-12.pdf) and double-wide-cas
> (cmpxchg16b on x86-64). So I have three questions for this list:
>
> 1) Would there be interest in adding such a type to the Boost smart 
> pointers?

I (and many others) will be very, very interested in your implementation, 
doubly so if you implement it using the interface proposed in

http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2007/n2297.html#atomic

I can't guarantee that your implementation will make it into Boost since 
hazard pointers are rumored to be patent-encumbered.

> 2) Has someone already done this?

If you google :-) for Joe Seigh's atomic_ptr, you'll find his 
implementation. It doesn't implement the entire shared_ptr interface though, 
so your implementation will be unique in this regard.