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https://issues.apache.org/jira/browse/HDFS-1529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12990740#comment-12990740
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Todd Lipcon commented on HDFS-1529:
-----------------------------------
Hi Hairong. The difference between the handling in the two different methods is
this:
In waitForAckedSeqno, the user thread is just blocked on an hflush() or flush
before close - In this case throwing an exception will not leave the stream in
an inconsistent state, and matches what one might expect: interrupting a thread
blocked on IO will throw cause the thread to throw an exception. In
waitAndQueueCurrentPacket() if we return early from that wait without an
exception, we still leave the stream in a "correct" state. Keeping the
interruption state flagged means the user will see the exception on the next
operation.
Since you gave +1 I'll commit as is, and if we want to clean this up we can do
it separately.
> Incorrect handling of interrupts in waitForAckedSeqno can cause deadlock
> ------------------------------------------------------------------------
>
> Key: HDFS-1529
> URL: https://issues.apache.org/jira/browse/HDFS-1529
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs client
> Affects Versions: 0.22.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Blocker
> Fix For: 0.22.0
>
> Attachments: Test.java, hdfs-1529.txt, hdfs-1529.txt, hdfs-1529.txt
>
>
> In HDFS-895 the handling of interrupts during hflush/close was changed to
> preserve interrupt status. This ends up creating an infinite loop in
> waitForAckedSeqno if the waiting thread gets interrupted, since Object.wait()
> has a strange semantic that it doesn't give up the lock even momentarily if
> the thread is already in interrupted state at the beginning of the call.
> We should decide what the correct behavior is here - if a thread is
> interrupted while it's calling hflush() or close() should we (a) throw an
> exception, perhaps InterruptedIOException (b) ignore, or (c) wait for the
> flush to finish but preserve interrupt status on exit?
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