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

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-08-08 12:21:09

--- In boost_at_[hidden], scleary_at_j... wrote:
> > 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