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From "Michael McCandless (JIRA)" <>
Subject [jira] [Commented] (LUCENE-5002) Deadlock in DocumentsWriterFlushControl
Date Fri, 17 May 2013 12:01:21 GMT


Michael McCandless commented on LUCENE-5002:

The patch is terrifying looking yet seems necessary, and on beasting seems to work (but: we
have to either not use docValues, or prevent Lucene3x codec).

I think stop-the-world is perfectly fine here: it's not like apps are calling deleteAll 1000s
of times per second.

I even think it'd be fine if concurrent indexing threads hit strange exceptions, and we document
that you should not use other methods while deleteAll is invoked in one thread, as long as
we can guarantee this never leads to index corruption.  This is just like you can call IW.close
from one thread while other threads are still indexing but those other threads can hit strange

I'll open a new issue to somehow simplify IW's sync... it's a mess now.
> Deadlock in DocumentsWriterFlushControl
> ---------------------------------------
>                 Key: LUCENE-5002
>                 URL:
>             Project: Lucene - Core
>          Issue Type: Bug
>    Affects Versions: 4.3
>         Environment: OpenJDK 64-Bit Server VM (23.7-b01 mixed mode)
> Linux Ubuntu Server 12.04 LTS 64-Bit
>            Reporter: Sergiusz Urbaniak
>            Assignee: Simon Willnauer
>             Fix For: 5.0, 4.4, 4.3.1
>         Attachments: LUCENE-5002.patch, LUCENE-5002_test.patch
> Hi all,
> We have an obvious deadlock between a "MaybeRefreshIndexJob" thread
> calling ReferenceManager.maybeRefresh( and a
> "RebuildIndexJob" thread calling
> IndexWriter.deleteAll(
> Lucene wants to flush in the "MaybeRefreshIndexJob" thread trying to intrinsically lock
the IndexWriter instance at {{}} before notifyAll()ing the
> Simultaneously the "RebuildIndexJob" thread who already intrinsically locked the IndexWriter
instance at IndexWriter#deleteAll wait()s at {{}} for
the flush forever causing a deadlock.
> {code}
> "MaybeRefreshIndexJob Thread - 2" daemon prio=10 tid=0x00007f8fe4006000 nid=0x1ac2 waiting
for monitor entry [0x00007f8fa7bf7000]
>    java.lang.Thread.State: BLOCKED (on object monitor)
> 	at org.apache.lucene.index.IndexWriter.useCompoundFile(
> 	- waiting to lock <0x00000000f1c00438> (a org.apache.lucene.index.IndexWriter)
> 	at org.apache.lucene.index.DocumentsWriterPerThread.sealFlushedSegment(
> 	at org.apache.lucene.index.DocumentsWriterPerThread.flush(
> 	at org.apache.lucene.index.DocumentsWriter.doFlush(
> 	at org.apache.lucene.index.DocumentsWriter.flushAllThreads(
> 	at org.apache.lucene.index.IndexWriter.getReader(
> 	- locked <0x00000000f1c007d0> (a java.lang.Object)
> 	at org.apache.lucene.index.StandardDirectoryReader.doOpenFromWriter(
> 	at org.apache.lucene.index.StandardDirectoryReader.doOpenIfChanged(
> 	at org.apache.lucene.index.StandardDirectoryReader.doOpenIfChanged(
> 	at org.apache.lucene.index.DirectoryReader.openIfChanged(
> 	at
> 	at
> 	at
> 	at
> 	at jobs.MaybeRefreshIndexJob.timeout(
> "RebuildIndexJob Thread - 1" prio=10 tid=0x00007f903000a000 nid=0x1a38 in Object.wait()
>    java.lang.Thread.State: WAITING (on object monitor)
> 	at java.lang.Object.wait(Native Method)
> 	- waiting on <0x00000000f1c0c240> (a org.apache.lucene.index.DocumentsWriterFlushControl)
> 	at java.lang.Object.wait(
> 	at org.apache.lucene.index.DocumentsWriterFlushControl.waitForFlush(
> 	- locked <0x00000000f1c0c240> (a org.apache.lucene.index.DocumentsWriterFlushControl)
> 	at org.apache.lucene.index.DocumentsWriter.abort(
> 	- locked <0x00000000f1c05370> (a org.apache.lucene.index.DocumentsWriter)
> 	at org.apache.lucene.index.IndexWriter.deleteAll(
> 	- locked <0x00000000f1c00438> (a org.apache.lucene.index.IndexWriter)
> 	at jobs.RebuildIndexJob.buildIndex(
> {code}

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