[HIVE-22906] Redundant checkLock Mutex blocks concurrent Lock requests

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-1
• Component/s: Locking
• Assignee: Denys Kuzmenko
• Reporter: Denys Kuzmenko
• Created: 18/Feb/20 16:42
• Updated: 17/Nov/22 08:50
• Resolved: 11/Mar/20 11:39

Description

enqueueLocks is already serialising locks creation via (SELECT NL_NEXT FROM NEXT_LOCK_ID FOR UPDATE). Requested locks would be assigned 'W' state.

checkLock is iterating over the sorted set of conflicting locks below current EXT_LOCK_ID. It does handle the situation when there is conflicting lock with lower ID in 'W' state - lock request would be denied and retried later.