Subj : Re: thread control by mutex, predicates and conditions puzzle
To   : comp.programming.threads
From : David Schwartz
Date : Fri Jan 07 2005 07:35 pm


"roland" <roland@nospam.com> wrote in message 
news:LwBDd.40033$BO5.38686@news.chello.at...

> Jomu wrote:

>> What is this stop/start action thing? Do you want to freeze your
>> threads only at some points or wherever they happen to be when you stop
>> them?

> Say, your thread is blocking on IO.

    Why not just avoid blocking on I/O?

> Now an external thread that is in
> charge of master control needs to tell: quit and restart IO.
> But I do not want to cancel the entire thread! (Imagine I have other 
> valuable
> state information in my thrad.)

    How you do this depends upon the rest of your architecture, but 
basically you just remove the I/O from the list of I/Os that your I/O-doing 
threads use to decide what I/O to do.

> How should I go for it when I
> 1) want a single thread wide master control while still be able to
>    wait on different things during the threads lifetime
> 2) _and_ write code with portability in mind? (The IO clearly is
>    highly system dependant.)
>
> I would be very glad if you could point me to such a pattern, since
> I am too a bit concerned of the "thundering herd" problem my broadcast
> could cause.

    Use non-blocking I/O. The threads that do I/O keep state on what I/Os 
they're working on, and other threads can access that state information with 
suitable locks. You're setting things up to be much harder than they have to 
be.

    DS

.