Subj : Re: waiting on signals from multiple threads using pthreads
To   : comp.programming.threads
From : Gianni Mariani
Date : Sun Mar 13 2005 07:41 am

red0356@yahoo.com wrote:
> In our application, we have three (possibly more) worker threads
> performing some task and another thread which waits for completion of
> all three tasks from the worker threads.  All three worker threads are
> NOT synchronous and it is possible to have one worker thread complete
> multiple tasks before another worker thread completes one task.  The
> waiting thread must wait for all three worker threads to complete at
> least one task, before doing its job.  What is the best pthread
> implementation for this problem?
> 
> Thanks in advance for all replies.
> 

posix had a condition variable (combined with a mutex).

======= psuedo code (C++-ish) ==========

Mutex		mutex;
Conditional	cv( mutex );

void worker()
{

      while ( Work work = GetWork() )
      {
	work.Do();

	Lock 	lock( mutex );

         done_queue.insert( work );
	cv.Signal();
      }
}

void another()
{
      Lock lock( mutex );
      do (
         Work work = done_queue.pop();
	
         if ( ! work ) {
              if ( finished ) return;
              cv.Wait();
         } else {
              Unlock unlock( mutex );
              work.do_another();
         }

      } while ( 1 );
}

.