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copied!<p>You should check for new data as soon as <code>pthread_cond_wait</code> returns, and wait again if there's no new data. That can happen if you get a spurious wake (think of it as the kernel accidentally waking you up by dropping something heavy down the stairs), and it would be better to wait immediately instead of changing <code>workerWaiting</code> then unlocking and relocking the mutex twice before waiting again.</p> <p>An RAII lock type would make the code so much cleaner:</p> <pre><code> while(true) { while(true) { { scoped_lock l(&manager->mutex); if(/* new data available */) { /* copy new data from shared to thread memory */ } else break; } /* process the data in thread memory */ scoped_lock l(&manager->mutex); /* copy results back to shared memory */ } scoped_lock l(&manager->mutex); // check if we should continue running if(!manager->workerRunning) break; // wait for new data to arrive manager->workerWaiting = true; while (!/* new data available */) pthread_cond_wait(&manager->condition, &manager->mutex); manager->workerWaiting = false; } </code></pre> <p>Using <code>pthread_cancel</code> as Oleg suggests would simplify it even further.</p> <p>Following your edit to the code to handle spurious wake-ups, it becomes much simpler if you use RAII and restructure it:</p> <pre><code> while(true) { { scoped_lock l(&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) break; /* copy new data from shared to thread memory */ } /* process the data in thread memory */ scoped_lock l(&manager->mutex); /* copy results back to shared memory */ } return NULL; </code></pre> <p>Without something like scoped_lock, what happens if <code>/* copy new data from shared to thread memory */</code> or <code>/* process the data in thread memory */</code> throws an exception? You'll never unlock the mutex.</p> <p>The RAII type could be as simple as:</p> <pre><code>struct scoped_lock { explicit scoped_lock(pthrad_mutex_t* m) : mx(m) { pthread_mutex_lock(mx); } ~scoped_lock() { pthread_mutex_unlock(mx); } private: pthread_mutex_t* mx; scoped_lock(const scoped_lock&); scoped_lock operator=(const scoped_lock&); }; </code></pre>

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