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https://issues.apache.org/jira/browse/HDFS-15963?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Xiaoqiao He updated HDFS-15963:
-------------------------------
    Fix Version/s: 3.4.0
     Hadoop Flags: Reviewed
       Resolution: Fixed
           Status: Resolved  (was: Patch Available)

Committed to trunk. Thanks [~zhangshuyan] for your report and contribution! 
Thanks [~weichiu] for your reviews.

> 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
>  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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