Re: thread lock/unlock example

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-09-15 08:36:41

--- In boost_at_[hidden], Branko Èibej <branko.cibej_at_h...> wrote:
> I think this is a real problem, but you don't need to expose
> lock() and unlock() to solve it. Instead you have a lock-inverter
> class (which must be a friend of lock, yes, but I think that's
> justified in this case):

> Your example becomes:
> 
>   {
>     boost::lock lock(m);
>     for (int i = a.get(); i < 10; a.next())
>     {
>       <some code>
>       {
>         boost::invert_lock unlock(lock);
>         f();
>       }
>       <some code>
>     }
>   }

This just compounds the problem.  The inverter now locks you into the 
same scope requirements as the original lock, which will be just as 
big of a problem (very small, IMHO, but I think everyone's admitted 
that it can occur).  Further, this inverter is worse than the 
unsafe_lock<> approach because it can "invalidate" *ANY* lock 
removing *ALL* runtime checking in condition::wait().

Bill Kempf