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https://issues.apache.org/jira/browse/LUCENE-6989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15855601#comment-15855601
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ASF subversion and git services commented on LUCENE-6989:
---------------------------------------------------------

Commit f4e493a7665a7e305506acce505c90ed1b28684e in lucene-solr's branch 
refs/heads/branch_5_5 from [~thetaphi]
[ https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=f4e493a ]

LUCENE-6989: Backport MH-based unmapping for Java 9 support


> Implement MMapDirectory unmapping for coming Java 9 changes
> -----------------------------------------------------------
>
>                 Key: LUCENE-6989
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6989
>             Project: Lucene - Core
>          Issue Type: Task
>          Components: core/store
>            Reporter: Uwe Schindler
>            Assignee: Uwe Schindler
>              Labels: Java9
>             Fix For: 6.0, 5.5.4, 6.4
>
>         Attachments: LUCENE-6989-disable5x.patch, 
> LUCENE-6989-disable5x.patch, LUCENE-6989-fixbuild148.patch, 
> LUCENE-6989.patch, LUCENE-6989.patch, LUCENE-6989.patch, LUCENE-6989.patch, 
> LUCENE-6989-v2.patch, LUCENE-6989-v3-post-b148.patch, 
> LUCENE-6989-v3-post-b148.patch, LUCENE-6989-v3-testFixes.patch
>
>
> Originally, the sun.misc.Cleaner interface was declared as "critical API" in 
> [JEP 260|http://openjdk.java.net/jeps/260 ]
> Unfortunately the decission was changed in favor of a oficially supported 
> {{java.lang.ref.Cleaner}} API. A side effect of this change is to move all 
> existing {{sun.misc.Cleaner}} APIs into a non-exported package. This causes 
> our forceful unmapping to no longer work, because we can get the cleaner 
> instance via reflection, but trying to invoke it will throw one of the new 
> Jigsaw RuntimeException because it is completely inaccessible. This will make 
> our forceful unmapping fail. There are also no changes in Garbage collector, 
> the problem still exists.
> For more information see this [mailing list 
> thread|http://mail.openjdk.java.net/pipermail/core-libs-dev/2016-January/thread.html#38243].
> This commit will likely be done, making our unmapping efforts no longer 
> working. Alan Bateman is aware of this issue and will open a new issue at 
> OpenJDK to allow forceful unmapping without using the now private 
> sun.misc.Cleaner. The idea is to let the internal class sun.misc.Cleaner 
> implement the Runable interface, so we can simply cast to runable and call 
> the run() method to unmap. The code would then work. This will lead to minor 
> changes in our unmapper in MMapDirectory: An instanceof check and casting if 
> possible.
> I opened this issue to keep track and implement the changes as soon as 
> possible, so people will have working unmapping when java 9 comes out. 
> Current Lucene versions will no longer work with Java 9.



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