Subj : Re: pthread_cond_signal() semantics
To   : comp.programming.threads
From : Markus Elfring
Date : Mon Jan 10 2005 09:48 pm


"William Hoggarth" <nospam@nospam.nospam> schrieb im Newsbeitrag
news:v48Ed.23$IW2.8@newsfe1-gui.ntli.net...
> Thanks for the replies, let's see if I understand correctly:
>
> William Hoggarth wrote:
>
> > I have a thread with similar to the following:
> >
> >   while(1) {
> >     get_input();
> >
> >     pthread_mutex_lock(&mutex);
> >     copy_input_to_buffer();
> >     pthread_cond_signal(&cond);
> >     pthread_mutex_unlock(&mutex);
> >   }
>
> Ok, let's see if I understand this correctly.
>
> 1) pthread_cond_signal(&cond) simply marks the waiting thread as waiting
on
> the mutex ( as if it had just called pthread_mutex_lock() and not
> pthread_cond_wait() ).
>
> 2) pthread_mutex_unlock(&mutex) merely unlocks the mutex, allowing the
> thread to reaquire the lock before the waiting thread can do so.
>
> 3) the most sensible way to get the behaviour I want is to have another
> condition variable which signals when the data has been processed.
>
> Is this right?
>
> Thanks,
>
> William Hoggarth

.