[
https://issues.apache.org/jira/browse/HDFS-16033?focusedWorklogId=600421&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-600421
]
ASF GitHub Bot logged work on HDFS-16033:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 21/May/21 15:12
Start Date: 21/May/21 15:12
Worklog Time Spent: 10m
Work Description: yikf opened a new pull request #3042:
URL: https://github.com/apache/hadoop/pull/3042
### What changes were proposed in this pull request?
In `StatisticsDataReferenceCleaner`, Cleaner thread will be blocked if we
remove reference from ReferenceQueue unless the queue.enqueue` called but no
now.
As shown below, We call ReferenceQueue.remove() now while cleanUp, Call
chain as follow：
`StatisticsDataReferenceCleaner#queue.remove() -> ReferenceQueue.remove(0)
-> lock.wait(0)`
lock.wait(0) will waitting perpetual unless lock.notify/notifyAll be called,
But, lock.notifyAll is called when queue.enqueue only, so Cleaner thread will
be blocked.
**ThreadDump:**
```
"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f7afc088800
nid=0x2119 in Object.wait() [0x00007f7b00230000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x00000000c00c2f58> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
- locked <0x00000000c00c2f58> (a java.lang.ref.Reference$Lock)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)
```
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Issue Time Tracking
-------------------
Worklog Id: (was: 600421)
Remaining Estimate: 0h
Time Spent: 10m
> Fix issue of the StatisticsDataReferenceCleaner cleanUp
> -------------------------------------------------------
>
> Key: HDFS-16033
> URL: https://issues.apache.org/jira/browse/HDFS-16033
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs
> Affects Versions: 3.2.1
> Reporter: yikf
> Priority: Minor
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Cleaner thread will be blocked if we remove reference from ReferenceQueue
> unless the `queue.enqueue` called.
> ----
> As shown below, We call ReferenceQueue.remove() now while cleanUp, Call
> chain as follow：
> *StatisticsDataReferenceCleaner#queue.remove() ->
> ReferenceQueue.remove(0) -> lock.wait(0)*
> But, lock.notifyAll is called when queue.enqueue only, so Cleaner thread
> will be blocked.
>
> ThreadDump:
> {code:java}
> "Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f7afc088800
> nid=0x2119 in Object.wait() [0x00007f7b00230000]
> java.lang.Thread.State: WAITING (on object monitor)
> at java.lang.Object.wait(Native Method)
> - waiting on <0x00000000c00c2f58> (a java.lang.ref.Reference$Lock)
> at java.lang.Object.wait(Object.java:502)
> at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
> - locked <0x00000000c00c2f58> (a java.lang.ref.Reference$Lock)
> at
> java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153){code}
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