RE: What's a Mutex ? (Was: Re: Threads)

From: scleary_at_[hidden]
Date: 2000-08-08 10:26:57

> Issues such as re-entrancy (recursion) are an implementation detail, 
> not actually part of the definition of the term.  Same for the name 
> of the operations available, and to some extent the operations 
> available (for instance, a try_lock is not a requirement by the 
> definition of the term, but is a very useful implementation detail).

I still disagree.  An implementation detail is, by *my* definition anyway,
something that can change without requiring end-user code to be aware of the
change.  For example, run-time parameters can be stored in an .ini file, the
Registry, an XML file, or some proprietary format; one can write a
run_time_parameter class that uses any of these as its underlying storage,
and the user code wouldn't care (as long as all the run_time_parameter
classes had the same interface).

So end-user code should not *ever* have to care about implementation
details.

If I design a program framework that assumes it has a re-entrant mutex, and
then change the "implementation detail" so that the mutex is no longer
re-entrant, then my entire framework becomes full of deadlock possibilities.
Therefore, I argue that re-entrancy of a mutex is *not* an implementation
detail, but defines two sub-definitions of a general "mutex" definition.

Similar arguments hold for
try-locking/timed-try-locking/static-init/who-knows-what-else:).  Each of
these attributes change how the mutex can be used, not how it works; and
therefore introduce new sub-definitions of "mutex", not implementation
details.

IMO, of course.  :)

        -Steve