Re: Threads: monitors vs. primitives

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-08-11 17:43:23

--- In boost_at_[hidden], jsiek_at_l... wrote:
> William Kempf writes:
>  > mutex mx;
>  > condition cv(mx);
>  > mutex::lock lock(mx);
>  > 
>  > while (!full)  // Just to not cloud things with the predicate
>  >    lock.wait(cv);
>  > 
>  > You obviously can't wait on the cv unless the mutex is locked.  
Since 
>  > both the lock and the CV were constructed with the mutex it's 
>  > possible to throw an exception if the two aren't associated with 
the 
>  > same mutex (not as good as a compile time error, but better than 
>  > nothing).
> 
> Or how about this:
> 
> 
> mutex mx;
> condition cv;     // no mutex here
> 
> mutex::lock lock(mx);
> 
> while (!full)
>   lock.wait(cv);  // mutex comes from the lock
> 
> 
> Now it is impossible for the user to use the wrong mutex with the
> codition variable.

I'm not sure I follow.  How is the following prohibited?

mutex mx1;
mutex mx2;
condition cv;

mutex::lock lock1(mx1);
mutex::lock lock2(mx2);

while (!full)
{
   lock1.wait(cv);
   lock2.wait(cv);
}