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Subj : Re: pthread_cond_signal() semantics
To   : comp.programming.threads
From : William Hoggarth
Date : Sun Jan 09 2005 10:55 am

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

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