Page History

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• • L04 load-acquires the current 'list_p' value into 'mid'; the  the use of load-acquire is necessary to get the latest value release-stored by another thread; the current 'list_p' is updated by either a release-store or a cmpxchg'ed by another thread depending on the algorithm that made the update; only the release-store needs to match up with a load-acquire, but this code doesn't know whether release-store or cmpxchg was used.
  • L0[56] is the empty list check and the only time that false is returned by this function.
  • L08 tries to mark the next field in 'mid':
    • If marking is not successful, we loop around to try it all again.
    • If marking is successful, then 'next_p' contains mid's unmarked next field value.
    • L09 load-acquires the current 'list_p' value to see if it still matches 'mid':
      • If the list head has changed, then we unmark mid on L11 and try it all again.
      • Otherwise, 'mid' is returned via 'mid_p' and we return true.

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