Subj : Re: I write a multithread program with pthread, and meet a program
To   : comp.programming.threads
From : loic-dev
Date : Mon Apr 11 2005 01:56 am

Hello,

> Yes. If commenting the point 1 as you said:
> pthread_mutex_unlock(&mutex);
> // cout<<"------------thread start"<<endl; // comment this line out!
> while(true){
> It can work well.

> But I do not know why it works well after I comment the line.

You didn't say which OS/Pthreads implementation you are using. Is it
Linux/NPTL, by chance?

Notice that nothing is said about cout being a cancellation point or
not. A correct implementation should get this right. But you're surely
on the safe side if you explicitely disable cancellation where you are
writting on cout.

[ as a matter of fact, with Linux/NPTL v0.61 I got the following
uncaught exception: FATAL: exception not rethrown. The number of
threads created depends from run to run.  ]


> You said it should have a predicate associated to the condition
> variable.

Yes, correct. Because you might be subject to spurious wake-up.


> But the reason that I use a condition variable here is that I want to
> the new thread runs before the main thread call pthread_cancel() to
> stop it.
> If I do not use a condition variable, it is possible that the main
> thread start the new thread and call pthread_cancel() to stop it
before
> the new thread start to run.

Yes, yes I understand that already.  But theoritically, you might be
woken up by a spurious signal, even if your thread doesn't run yet.


Cheers,
Loic.

.