Change Details

- Enqueue the thread earlier in the loop to avoid missed wakeups. In particular, ensure that we call umtxq_insert() before attempting the CAS. - If the lock is unowned (i.e., owner == UMUTEX_CONTESTED), we might get a spurious failure, and in that case we need to retry the loop.

If the lock is unowned (i.e., owner == UMUTEX_CONTESTED), we might get a spurious failure, and in that case we need to retry the loop.

- EnqueueIf the thread earlier in the loop to avoid missed wakeups. Inlock is unowned (i.e., owner == UMUTEX_CONTESTED), we might get a particular, ensure that we call umtxq_insert() before attempting the CAS. - If the lock is unowned (i.e., owner == UMUTEX_CONTESTED), we might get a spurious failure, and in that case we need to retry the loop.