al_lock_mutex - Allegro 5 API

       Acquire  the  lock on mutex.  If the mutex is already locked by another thread, the call will block until
       the mutex becomes available and locked.

       If the mutex is already locked by the calling thread, then the behaviour depends on whether the mutex was
       created with al_create_mutex(3alleg5) or al_create_mutex_recursive(3alleg5).  In  the  former  case,  the
       behaviour  is  undefined;  the  most  likely behaviour is deadlock.  In the latter case, the count in the
       mutex will be incremented and the call will return immediately.

       al_lock_mutex - Allegro 5 API

al_unlock_mutex(3alleg5).

       Wedon’tyethaveal_mutex_trylock.

Allegro reference manual                                                                  al_lock_mutex(3alleg5)

              #include <allegro5/allegro.h>

              void al_lock_mutex(ALLEGRO_MUTEX *mutex)