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https://issues.apache.org/jira/browse/HBASE-7728?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13569544#comment-13569544
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ramkrishna.s.vasudevan commented on HBASE-7728:
-----------------------------------------------

bq.For sync'ing you're right. It makes no sense to sync the new writer.
Why do you feel so Lars? Is it because anyway it would get synced in the 
subsequent sync calls?
                
> deadlock occurs between hlog roller and hlog syncer
> ---------------------------------------------------
>
>                 Key: HBASE-7728
>                 URL: https://issues.apache.org/jira/browse/HBASE-7728
>             Project: HBase
>          Issue Type: Bug
>          Components: wal
>    Affects Versions: 0.94.2
>         Environment: Linux 2.6.18-164.el5 x86_64 GNU/Linux
>            Reporter: Wang Qiang
>            Assignee: Ted Yu
>            Priority: Blocker
>             Fix For: 0.96.0, 0.94.5
>
>         Attachments: 7728-0.94-simplified.txt, 7728-0.94.txt, 
> 7728-0.94-v2.txt, 7728-suggest-0.96.txt, 7728-suggest.txt, 7728-v1.txt, 
> 7728-v2.txt, 7728-v3.txt, 7728-v4.txt
>
>
> the hlog roller thread and hlog syncer thread may occur dead lock with the 
> 'flushLock' and 'updateLock', and then cause all 'IPC Server handler' thread 
> blocked on hlog append. the jstack info is as follow :
> "regionserver60020.logRoller":
>         at 
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1305)
>         - waiting to lock <0x000000067bf88d58> (a java.lang.Object)
>         at 
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1283)
>         at org.apache.hadoop.hbase.regionserver.wal.HLog.sync(HLog.java:1456)
>         at 
> org.apache.hadoop.hbase.regionserver.wal.HLog.cleanupCurrentWriter(HLog.java:876)
>         at 
> org.apache.hadoop.hbase.regionserver.wal.HLog.rollWriter(HLog.java:657)
>         - locked <0x000000067d54ace0> (a java.lang.Object)
>         at 
> org.apache.hadoop.hbase.regionserver.LogRoller.run(LogRoller.java:94)
>         at java.lang.Thread.run(Thread.java:662)
> "regionserver60020.logSyncer":
>         at 
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1314)
>         - waiting to lock <0x000000067d54ace0> (a java.lang.Object)
>         - locked <0x000000067bf88d58> (a java.lang.Object)
>         at 
> org.apache.hadoop.hbase.regionserver.wal.HLog.syncer(HLog.java:1283)
>         at org.apache.hadoop.hbase.regionserver.wal.HLog.sync(HLog.java:1456)
>         at 
> org.apache.hadoop.hbase.regionserver.wal.HLog$LogSyncer.run(HLog.java:1235)
>         at java.lang.Thread.run(Thread.java:662)

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