More Lock Manager Logic
On lock release (OID, XID):
- Update list of Xacts holding lock.
- Examine head of wait queue.
- If Xact there can run, add it to list of Xacts holding lock (change mode as needed).
- Repeat until head of wait queue cannot be run.
Note: Lock request handled atomically!
- via latches (i.e. semaphores/mutex; OS stuff).