1) set the 'list_op_pending' word to the address of the 'lock entry'
to be removed,
2) remove the lock entry for this lock from the 'head' list,
- 2) release the futex lock, and
- 2) clear the 'lock_op_pending' word.
+ 3) release the futex lock, and
+ 4) clear the 'lock_op_pending' word.
On exit, the kernel will consider the address stored in
'list_op_pending' and the address of each 'lock word' found by walking