title: Why is `pthread_mutex_lock` needed when `pthread_mutex_trylock` is there?
body: <p><code>pthread_mutex_trylock</code> detects deadlocks, doesn't block, then why would you even <em>"need"</em> <code>pthread_mutex_lock</code>?</p>
  
  <p>Perhaps when you deliberately want the thread to block? But in that case it may result in a deadlock?</p>