[HBASE-16063] Race condition in new FIFO fastpath from HBASE-16023

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 1.3.0
• Component/s: Scheduler
• Assignee: Unassigned
• Reporter: Michael Stack
• Created: 18/Jun/16 00:24
• Updated: 17/May/19 15:59

Description

From ikeda over in HBASE-16023 at https://issues.apache.org/jira/browse/HBASE-16023?focusedCommentId=15331172&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15331172

An concrete example of the race condition:
1. Worker checks no task.
2. Reader checks no ready handler.
3. Worker pushes itself as a ready handler and waits on the semaphore.
4. Reader queues a task to the queue, without directly passing it to the ready handler nor releasing the semaphore.
(1,3) and (2,4) should be exclusively executed. That depends on luck, and it might be not severe