Synchronize threads for pthread_cond_broadcast call

Question

I have a simple application with a "manager" thread that spawns ten simple "worker" threads. I want all of the "worker" threads to block on the same condition variable (ie: condvar), and I want to manually signal all ten threads to wake up at the same time with a pthread_cond_broadcast call.

In the case of my application, it is possible for threads to suffer an error condition and terminate early, so it is possible that not all ten threads make it to the synchronization point.

One simple mechanism would be to create a pthread_barrier_t and have all ten threads call pthread_barrier_wait, and when all ten threads complete this call, they are all free to continue execution. However, this would require the threads being able to modify the number of threads the barrier requires to unblock. I don't know if this can be safely modified.

Additionally, I want to guarantee all the still-working threads not start automatically like they would with a barrier, I want to manually start them with a pthread_cond_broadcast call instead. How would I guarantee that all the threads that are still alive (ideally ten) have blocked on the condvar before I made the broadcast call?

Thanks!