Yeah. Event at runtime, it seems possible when the owner thread gives up the ownership (by setting owner_tid = 0) can use an extra flag to let other threads to

Yeah. Event at runtime, it seems possible when the owner thread gives up the ownership (by setting owner_tid = 0) can use an extra flag to let other threads to compete for the ownership. As long as the flag is on the 2nd half-word, (it seems) there is no atomic requirement for the 1st half-word.