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https://issues.apache.org/jira/browse/HDFS-17334?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17808076#comment-17808076
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ASF GitHub Bot commented on HDFS-17334:
---------------------------------------
hfutatzhanghb commented on PR #6434:
URL: https://github.com/apache/hadoop/pull/6434#issuecomment-1898012100
> > > Line211 has already ensured that we have a monitor for this object:
> > >
https://github.com/apache/hadoop/blob/ba6ada73acc2bce560878272c543534c21c76f22/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FSEditLogAsync.java#L211-L223
> > >
> > > So, I think the description in this PR is not a problem. What's your
opinion? @hfutatzhanghb
> >
> >
> > @zhangshuyan0 Sir, `this.wait(1000);` is in do-while loop, when we
invoke `this.wait(1000)` at first time, it will release object monitor. But in
extreme situation, it will throw Exception when invoke `this.wait(1000)` at the
second time, because current thread does not hold the object monitor. Waiting
for your response~
>
> Let's see [java
doc](https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-)
:
>
> > Thus, on return from the wait method, the synchronization state of the
object and of thread T is exactly as it was when the wait method was invoked.
>
> Therefore, after `this.wait(1000)` returns at first time, it obtains the
monitor again. I think no exception will be thrown here. By the way, in this
[java
doc](https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#wait-long-)
, `synchronized -> while loop` is showed as a recommended usage. Looking
forward to your response.
Sir, Thanks a lot for your explanations here. I will close this PR laterly.
Thanks again.
> FSEditLogAsync#enqueueEdit does not synchronized this before invoke wait
> method
> -------------------------------------------------------------------------------
>
> Key: HDFS-17334
> URL: https://issues.apache.org/jira/browse/HDFS-17334
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: namenode
> Affects Versions: 3.3.6
> Reporter: farmmamba
> Assignee: farmmamba
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.5.0
>
>
> In method FSEditLogAsync#enqueueEdit , there exist the below codes:
> {code:java}
> if (Thread.holdsLock(this)) {
> // if queue is full, synchronized caller must immediately relinquish
> // the monitor before re-offering to avoid deadlock with sync thread
> // which needs the monitor to write transactions.
> int permits = overflowMutex.drainPermits();
> try {
> do {
> this.wait(1000); // will be notified by next logSync.
> } while (!editPendingQ.offer(edit));
> } finally {
> overflowMutex.release(permits);
> }
> } {code}
> It maybe invoke this.wait(1000) without having object this's monitor.
>
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