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POPThread beginner - starting, syncing, stopping a worker thread
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copied!<p>I have the following manager<->worker situation:</p> <pre><code>class Manager { private: pthread_attr_t workerSettings; pthread_t worker; pthread_cond_t condition; pthread_mutex_t mutex; bool workerRunning; static void* worker_function(void* args) { Manager* manager = (Manager*)args; while(true) { while(true) { pthread_mutex_lock(&manager->mutex); if(/* new data available */) { /* copy new data from shared to thread memory */ pthread_mutex_unlock(&manager->mutex); } else { pthread_mutex_unlock(&manager->mutex); break; } /* process the data in thread memory */ pthread_mutex_lock(&manager->mutex); /* copy results back to shared memory */ pthread_mutex_unlock(&manager->mutex); } pthread_mutex_lock(&manager->mutex); // wait for new data to arrive while(manager->workerRunning && !/* new data available*/) pthread_cond_wait(&manager->condition, &manager->mutex); // check if we should continue running if(!manager->workerRunning) { pthread_mutex_unlock(&manager->mutex); break; } pthread_mutex_unlock(&manager->mutex); } pthread_exit(NULL); return NULL; // just to avoid the missing return statement compiler warning } public: Manager() : workerRunning(true) { pthread_cond_init(&condition, NULL); pthread_mutex_init(&mutex, NULL); pthread_attr_init(&workerSettings); pthread_attr_setdetachstate(&workerSettings, PTHREAD_CREATE_JOINABLE); pthread_create(&worker, &workerSettings, worker_function, (void*)this); } // this *may* be called repeatedly or very seldom void addData(void) { pthread_mutex_lock(&mutex); /* copy new data into shared memory */ pthread_cond_signal(&condition); pthread_mutex_unlock(&mutex); } ~Manager() { // set workerRunning to false and signal the worker pthread_mutex_lock(&mutex); workerRunning = false; pthread_cond_signal(&condition); pthread_mutex_unlock(&mutex); // wait for the worker to exit pthread_join(worker, NULL); // cleanup pthread_attr_destroy(&workerSettings); pthread_mutex_destroy(&mutex); pthread_cond_destroy(&condition); } }; </code></pre> <p>I'm not completely sure about this at several places:</p> <ul> <li>Is the fact that Manager spawns a new thread in its constructor considered a bad practice? (I will only have one Manager object, so i guess that should be fine)</li> <li>What about the pthread_exit - i see this in many tutorials but i don't quite get why it should be there? Can't i simply return the function to exit the thread? I also think the return NULL is dead code, but gcc warns when it's missing because it obviously can't know that pthread_exit already killed the thread at that point.</li> <li>About the constructor - can i destroy the thread attr object (workerSettings) immediately after spawning the thread or does it have to stay valid for the entire lifetime of the thread?</li> <li>About the destructor: Is this the right way to do this?</li> </ul> <p>And most importantly:</p> <ul> <li>Do your experienced eyes see any synchronization issues there?</li> </ul> <p>Thanks for your help!</p>

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