return -EFAULT;
        }
 
-       lock_kernel();
-
+       mutex_lock(&port->port.mutex);
        change_speed = ((port->port.flags & ASYNC_SPD_MASK) !=
                        (tmp.flags & ASYNC_SPD_MASK));
        change_speed |= (tmp.custom_divisor != port->custom_divisor);
                    ((tmp.flags & ~ASYNC_USR_MASK) !=
                     (port->port.flags & ~ASYNC_USR_MASK))) {
                        func_exit();
-                       unlock_kernel();
+                       mutex_unlock(&port->port.mutex);
                        return -EPERM;
                }
                port->port.flags = ((port->port.flags & ~ASYNC_USR_MASK) |
                sx_change_speed(bp, port);
 
        func_exit();
-       unlock_kernel();
+       mutex_unlock(&port->port.mutex);
        return 0;
 }
 
        func_enter();
 
        memset(&tmp, 0, sizeof(tmp));
-       lock_kernel();
+       mutex_lock(&port->port.mutex);
        tmp.type = PORT_CIRRUS;
        tmp.line = port - sx_port;
        tmp.port = bp->base;
        tmp.closing_wait = port->port.closing_wait * HZ/100;
        tmp.custom_divisor =  port->custom_divisor;
        tmp.xmit_fifo_size = CD186x_NFIFO;
-       unlock_kernel();
+       mutex_unlock(&port->port.mutex);
        if (copy_to_user(retinfo, &tmp, sizeof(tmp))) {
                func_exit();
                return -EFAULT;