Re: Thread Checking the Queue data in an infinite loop

From:
"Doug Harrison [MVP]" <dsh@mvps.org>
Newsgroups:
microsoft.public.vc.mfc
Date:
Sat, 12 Jan 2008 16:13:19 -0600
Message-ID:
<ondio3d6p8bbv372f90r2tk53dhnvfbmnm@4ax.com>
On Sat, 12 Jan 2008 14:14:04 -0500, Joseph M. Newcomer
<newcomer@flounder.com> wrote:

2) Use of Event Synchronization is not perfect. Should i not go ahead
with it?

*****
Why? If it isn't perfect, why not choose a solution that is "out of the box" correct,
such as I/O Completion ports. I'd not even consider it, let alone think that it was worth
the effort to make it work. If this code came past my desk, I'd rip the event
synchronization out immediately. Since I would find it deeply suspect, I'd assume that
any malfunction of the program was due to bugs in it, and I'd replace it immediately with
something that is known to work well.


How is an I/O Completion port better than what the OP proposed, assuming he
implements the changes I mentioned in my reply to him? Here's the modified
algorithm, in pseudocode:

Reader (sole):

while (!done)
{
   ev.wait();
   mx.lock();
   // NB: He said he is fine with draining the queue.
   if (!q.empty())
      q.drain();
   mx.unlock();
}

Writer (many):

mx.lock();
q.push();
mx.unlock();
ev.set();

How do IOCPs improve on this?

--
Doug Harrison
Visual C++ MVP

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