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copied!<p>Your <code>anotherThread</code> simply calls <code>pthread_cond_wait</code> without first testing whether the desired condition (counter reaching ten) has already happened. This is incorrect logic, which will lead to the <em>lost wakeup problem</em>: the name of a recurring bug that plagues incorrectly written multithreaded programs.</p> <p>Condition variables are stateless. If <code>pthread_cond_signal</code> or <code>pthread_cond_broadcast</code> is called on a condition on which no threads are currently waiting, the operation has no effect. It is not remembered. So it is possible for your signaling thread to count to <code>10</code> very quickly, and signal the condition variable, before the other thread has reached the <code>pthread_cond_wait</code> call.</p> <p>You need a loop around <code>pthread_cond_wait</code>. The condition must be checked in case it is already true, so that the thread does not wait for a wakeup which already happened. And it should be a loop because wakeups can be spurious: just because the thread falls through the <code>pthread_cond_wait</code> doesn't mean that the condition is actually true:</p> <pre><code>while (cont < 10) pthread_cond_wait(&cond, &myMutex); </code></pre> <p>Also, there is no need to create a thread attribute just to make a thread joinable. This is the default situation when you use a null pointer for the creation attribute. POSIX threads are joinable unless created detached, or converted to detached with <code>pthread_detach</code>.</p> <p>Another thing: whenever possible, avoid calling <code>pthread_cond_signal</code> while holding a mutex lock. It's not incorrect, but it's potentially wasteful, because the operation may actually have to call into the OS kernel to wake up a thread, and so you're holding this expensive mutex lock over the entire system call (when all you really need it for is protecting a few machine instructions that working with shared data in your application).</p>

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