Re: [boost] Re: TR2 and C++0x heads up

From: Peter Dimov (pdimov_at_[hidden])
Date: 2005-04-27 18:06:48

Matt Hurd wrote:
>> Peter Dimov <pdimov_at_[hidden]> wrote:
>> The canonical definition of "lock free" is that the system as a
>> whole always makes progress. An ordinary lock-based algorithm does
>> not have this property; if the thread that obtained the lock
>> suddenly dies, no other thread can move past that lock.
>
> Thanks for clearing up the definition.  Though I do find it confusing
> as I've seen people call stuff lock-free where the approach uses
> versioning and retry semantics based on an optimistic concurrency
> approach.

This can still be lock-free; even though a particular thread is not 
guaranteed to make progress, _some_ thread is.

When every thread is guaranteed to make progress in a finite number of steps 
the algorithm is called "wait-free".