Re: Threads: what I wrote...

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-08-09 17:35:51

--- In boost_at_[hidden], jpanzer_at_n... wrote:
> Jens Maurer wrote:
> 
> > Dietmar Kuehl wrote:
> > >   <http://www.dietmar-kuehl.de/threads/>
> >
> > I've read through the paper.
> >
> > For avoiding race conditions, it focuses very much on
> > mutexes and locks.  However, there seems to be a (growing)
> > set of data structures available which do not require any
> > locks. For example, a lock-free (yet fully thread-safe)
> > single-linked list can be achieved when a few atomic CPU
> > instructions are available (only).
> >
> > While this is probably system specific, I wonder whether
> > such atomic operations can be presented in a portable
> > interface so as to promote portable implementations of
> > lock-free data structures.
> 
> Atomic increment and decrement could be really useful
> for reference counting.

Don't forget atomic exchange, though it can lead to improper useage 
by someone who doesn't understand concurrency issues.

> However, I worry that not all systems could implement such
> atomic operations efficiently without some piece of
> auxiliary storage.  Is this an unfounded worry?

An "atomic counter" can be implemented on all systems for which a 
mutex can be implemented.  If the system doesn't support the 
underlying primitives you simply build them by using a mutex.  No 
where near as efficient, but it solves the problem of portability.