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https://issues.apache.org/jira/browse/HDFS-15963?focusedWorklogId=586311&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-586311
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ASF GitHub Bot logged work on HDFS-15963:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 21/Apr/21 04:38
            Start Date: 21/Apr/21 04:38
    Worklog Time Spent: 10m 
      Work Description: zhangshuyan0 opened a new pull request #2941:
URL: https://github.com/apache/hadoop/pull/2941


   HDFS-15963. Unreleased volume references cause an infinite loop. (#2889) 
Contributed by Shuyan Zhang.
   
   Reviewed-by: Wei-Chiu Chuang <weic...@apache.org>
   Reviewed-by: He Xiaoqiao <hexiaoq...@apache.org>
   


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Issue Time Tracking
-------------------

    Worklog Id:     (was: 586311)
    Time Spent: 4h 10m  (was: 4h)

> Unreleased volume references cause an infinite loop
> ---------------------------------------------------
>
>                 Key: HDFS-15963
>                 URL: https://issues.apache.org/jira/browse/HDFS-15963
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>            Reporter: Shuyan Zhang
>            Assignee: Shuyan Zhang
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 3.4.0
>
>         Attachments: HDFS-15963.001.patch, HDFS-15963.002.patch, 
> HDFS-15963.003.patch
>
>          Time Spent: 4h 10m
>  Remaining Estimate: 0h
>
> When BlockSender throws an exception because the meta-data cannot be found, 
> the volume reference obtained by the thread is not released, which causes the 
> thread trying to remove the volume to wait and fall into an infinite loop.
> {code:java}
> boolean checkVolumesRemoved() {
>   Iterator<FsVolumeImpl> it = volumesBeingRemoved.iterator();
>   while (it.hasNext()) {
>     FsVolumeImpl volume = it.next();
>     if (!volume.checkClosed()) {
>       return false;
>     }
>     it.remove();
>   }
>   return true;
> }
> boolean checkClosed() {
>   // always be true.
>   if (this.reference.getReferenceCount() > 0) {
>     FsDatasetImpl.LOG.debug("The reference count for {} is {}, wait to be 0.",
>         this, reference.getReferenceCount());
>     return false;
>   }
>   return true;
> }
> {code}
> At the same time, because the thread has been holding checkDirsLock when 
> removing the volume, other threads trying to acquire the same lock will be 
> permanently blocked.
> Similar problems also occur in RamDiskAsyncLazyPersistService and 
> FsDatasetAsyncDiskService.
> This patch releases the three previously unreleased volume references.



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