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https://issues.apache.org/jira/browse/DERBY-700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12706621#action_12706621
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Kathey Marsden commented on DERBY-700:
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I did some testing with the thread name idea (just in a separate stand-alone
program) and found that it would probably be workable. Performance wasn't bad.
It seemed to take only 16 milliseconds on my machine to iterate through 1000
thread names and synchronizing on an interned string seemed to work across
ClassLoaders but ...
1) It would require RuntimePermissions getStackTrace and modifyThreadGroup to
derby.jar, which seem like pretty powerful additions to our permissions
requirements.
2) I was looking back at Suresh's original implmentation (using the system
property) and found that solution actually still holds promise. There was just
an issue with synchronization which needs to be resolved. This solution
wouldn't collide with any effort to consolidate the daemon threads and we
already have this permission requirement documented, so I think this is a
cleaner solution that should be revisited.
I'll take a look again at the old patch and try to figure out why the
synchronization expansion was required and how to avoid it.
> Derby does not prevent dual boot of database from different classloaders on
> Linux
> ---------------------------------------------------------------------------------
>
> Key: DERBY-700
> URL: https://issues.apache.org/jira/browse/DERBY-700
> Project: Derby
> Issue Type: Bug
> Components: Store
> Affects Versions: 10.0.2.0, 10.0.2.1, 10.1.1.0, 10.1.2.1, 10.1.3.1,
> 10.2.1.6, 10.2.2.0, 10.3.1.4, 10.4.1.3
> Environment: ava -version
> java version "1.4.2_08"
> Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.2_08-b03)
> Java HotSpot(TM) Client VM (build 1.4.2_08-b03, mixed mode)
> Reporter: Kathey Marsden
> Priority: Critical
> Attachments: DERBY-700.diff, DERBY-700.stat,
> derby-700_06_07_07_diff.txt, derby-700_06_07_07_stat.txt,
> derby-700_06_19_2007, derby-700_diff.txt, derby-700_stat.txt,
> DERBY-700_v1_use_to_run_DualBootrepro_multithreaded.diff,
> DERBY-700_v1_use_to_run_DualBootrepro_multithreaded.stat,
> derby-700_with_NPE_fix_diff.txt, derby-700_with_NPE_fix_stat.txt, derby.log,
> derby700_singleproperty_v1.diff, derby700_singleproperty_v1.stat,
> DualBootRepro.java, DualBootRepro2.zip, DualBootRepro_mutltithreaded.tar.bz2,
> releaseNote.html, releaseNote.html
>
>
> Derby does not prevent dual boot from two different classloaders on Linux.
> To reproduce run the program DualBootRepro with no derby jars in your
> classpath. The program assumes derby.jar is in 10.1.2.1/derby.jar, you can
> change the location by changing the DERBY_LIB_DIR variable.
> On Linux the output is:
> $java -cp . DualBootRepro
> Loading derby from file:10.1.2.1/derby.jar
> 10.1.2.1/derby.jar
> Booted database in loader java.net.urlclassloa...@8ed465
> FAIL: Booted database in 2nd loader java.net.urlclassloa...@dc6a77
> On Windows I get the expected output.
> $ java -cp . DualBootRepro
> Loading derby from file:10.1.2.1/derby.jar
> 10.1.2.1/derby.jar
> Booted database in loader java.net.urlclassloa...@1ac04e8
> PASS: Expected exception for dualboot:Another instance of Derby may have
> already booted the database D:\marsden\repro\dualboot\mydb.
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