Re: A simple monitor for Boost

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-08-10 10:36:37

--- In boost_at_[hidden], "William Kempf" <sirwillard_at_m...> wrote:
> --- In boost_at_[hidden], "Greg Colvin" <gcolvin_at_u...> wrote:
> > From: "William Kempf" <sirwillard_at_m...>
> > > --- In boost_at_[hidden], "Greg Colvin" <gcolvin_at_u...> wrote:
> > > > What is the simplest, safest language construct we know of 
for 
> managing
> > > > concurrent access to data?  I would say the monitor, as 
> developed and
> > > > described by Per Hansen and Tony Hoare in the 1970s, and 
> implemented in
> > > > many programming languages since then.  The classic 1974 
paper 
> by Hoare
> > > > remains one of the best introductions
> > > >    http://www.acm.org/classics/feb96/
> > > > and Hansen's 1993 review is also very useful
> > > >    
http://www.acm.org/pubs/citations/proceedings/plan/154766/p1-
>  hansen/

I've taken a look at the classic 1974 paper by Hoare, and this paper 
has a very good example of why the simplistic monitor you've 
described can not be a replacement for conditions.  He's got an 
example of a read/write lock implemented using his concept of a 
monitor.  The implementation requires two conditions.  I'm not sure 
that a monitor deserves first class implementation in a C++ library 
given this.  The monitor as Hoare describes it may simply be a 
programming idiom used with mutexes and conditions.  That's 
definately something that's up to debate, but I think I've proven to 
myself that we can't do with out the primitives mutex and condition 
just because we include a monitor.

I tried to look at Hansen's 1993 review, but I'm no longer an ACM 
member and so don't have access to it.  (I dropped membership after 
graduating in '92).

William Kempf