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Posted to issues@hbase.apache.org by "ramkrishna.s.vasudevan (JIRA)" <ji...@apache.org> on 2012/11/16 16:54:12 UTC
[jira] [Assigned] (HBASE-7160) Improve IdLock and remove its minor
defects
[ https://issues.apache.org/jira/browse/HBASE-7160?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
ramkrishna.s.vasudevan reassigned HBASE-7160:
---------------------------------------------
Assignee: Hiroshi Ikeda
> Improve IdLock and remove its minor defects
> -------------------------------------------
>
> Key: HBASE-7160
> URL: https://issues.apache.org/jira/browse/HBASE-7160
> Project: HBase
> Issue Type: Improvement
> Reporter: Hiroshi Ikeda
> Assignee: Hiroshi Ikeda
> Priority: Minor
> Attachments: HBASE-7160.patch
>
>
> Combination of synchronizations and concurrent collections complicates the code, and it is hard to trace the code and to confirm its correctness. We should re-create the class and make it more understandable.
> In the current code, I find the following minor defects:
> (1) In the case that there is a waiting thread for a lock in getLockEntry() and another thread is releasing the lock by calling releaseLockEntry(), trying to get the lock with a 3rd thread by calling getLockEntry() falls into a busy loop until the waiting thread wakes up and gets the lock.
> Even if notify() wakes up the blocked thread and causes a context switch to the waked thread immediately, synchronization might block the waked thread and cause another context switch, and the busy loop might continue for a while.
> (2) In the same case as (1), since releasing the lock is merely notifying without removing the lock-entry from the map, interrupting the waiting thread might leave an unused lock-entry (entry.numWaiters == 0) in the map. This is a memory leak unless the id of the lock is used again.
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