Subj : Re: Insane "Metered Section" example on MSDN
To   : comp.programming.threads
From : Joe Seigh
Date : Tue Apr 19 2005 08:09 am

On 19 Apr 2005 01:48:36 -0700, Agresao <agresao@yahoo.com> wrote:

> I was trying to implement a semaphore that won't always do a kernel
> transition to a Win32 object and came up with some code that seemed to
> work. Then I found this article on MSDN about this thing called a
> "metered section":
>
> http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dndllpro/html/msdn_metrsect.asp
>
> The code sample looked very similar to my own efforts which sort of
> made me think that my solution was correct. However by thinking a
> little deeper one realizes that their design has a terrible race
> condition, in which threads are blocked waiting for an auto-reset event
> to be signaled when there's nobody to signal it. Testing showed that
> this actually happens.
>
> I'm sure some of you have seen this article before and talked about it,
> but what puzzles me is that it has been in MSDN since 1998 and nobody
> has bothered to revise it...
>
>
There's a lot bad examples on MSDN.  Almost anything to do with using
Events as condition variables is probably wrong.  For a semaphore
that doesn't do a kernel call unless it needs to block see

http://groups.google.com/groups?selm=412F5D8D.416AE16A@xemaps.com

-- 
Joe Seigh

When you get lemons, you make lemonade.
When you get hardware, you make software.

.