+ * Lock this mutex.
+ * If the mutex is currently unlocked, it becomes locked and owned by
+ * the calling thread. If the mutex is already locked by another thread,
+ * the calling thread is suspended until the mutex is unlocked. If the
+ * mutex is already locked and owned by the calling thread, the calling
+ * thread is suspended until the mutex is unlocked, effectively causing
+ * the calling thread to deadlock.
+ *
+ * @see SGMutex::trylock