From: Tassilo Horn <heimdall@...>
Date: 2004-10-09T02:04:54+09:00
Subject: Re: Problems with my first multithreaded Rupy programm

"SER" <ser@germane-software.com> writes:

> A couple of things.

Perfect. I'm willing to learn.

> 1) Create the Waiter last.  He's got the lock on the mutex, so none of
> the other threads can enter their synchronized sections, so they can't
> wait.  They're simply blocking while waiting to enter the protected
> section.  It doesn't matter that the waiter is sleep()ing, because he
> still has the lock.  If you create the waiter last, then everybody else
> has a chance to enter a synchronized section and wait (releasing the
> lock) before the waiter does his thing.

Ah, I understand.

> 2) Don't use Thread.stop.  It isn't doing what I think you think it is
> doing.

I was quite sure it's not doing what I wanted it to do but had no better
idea how to do what I want it to do. ;-)

> 3) Create another CV just for the waiter, so you can send signals
> directly to him

And that is the solution for 2) which I didn't realize.

> 4) Wrap your "whiles" in the synchronized sections, not the other way
> around.  For one thing, entering synchronized sections are costly; you
> want to do it as rarely as you can.  For another, when you wait(), you
> release the lock, allowing others to get at the lock, so it is OK to
> put the while inside the synchronized section.

Ok.

> 5) If I was going to clean up the code for you, I'd recommend doing
> something like this:

Oh, thanks. I hope I'll be disciplinated enough to first implementing
your tips on my own before reading you code...

Much thanks for your great help. But _one_ posting would have been
enough! ;-)

Regards,
Tassilo