to be inserted,
2) acquire the futex lock,
3) add the lock entry, with its thread id (TID) in the bottom 29 bits
of the 'lock word', to the linked list starting at 'head', and
4) clear the 'list_op_pending' word.
to be inserted,
2) acquire the futex lock,
3) add the lock entry, with its thread id (TID) in the bottom 29 bits
of the 'lock word', to the linked list starting at 'head', and
4) clear the 'list_op_pending' word.