Re: [boost] Re: Threads: monitors vs. primitives

From: Greg Colvin (gcolvin_at_[hidden])
Date: 2000-08-11 15:41:17

From: "William Kempf" <sirwillard_at_[hidden]>
> ...
> > > I also don't know why you used a class for waiting.  The only 
> benefit 
> > > this gave you in your example was the fact that you could name 
> the 
> > > wait.  However, the CV and predicate should have been enough for 
> this.
> > 
> > The main benefit is that the wait destructor signals the
> > condition.  So the wait class privides a shorthand for:
> > 
> >     while (predicate())
> >         entry_condition.wait();
> >     try {
> > 
> >        // ...
> > 
> >     } catch (...) {
> >        exit_condition.signal();
> >        throw;
> >     }    
> >     condition.signal();
        ^^^^^^^^^
Typo:   ^^^^^^^^^
        exit_condition        
 
> *confused*  Why should you signal the condition after waiting for 
> it?  That sounds to me like you'll just wind up with a "busy wait" 
> when you have multiple threads waiting on the condition.  Or am I 
> missing something?