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https://issues.apache.org/jira/browse/DERBY-700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12505957
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Kathey Marsden commented on DERBY-700:
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I am working to move the intraJVM lock into StorageFile, getExclusiveLock()/
releaseExclusiveLock, but I wanted to comment on why I expanded the
synchronization to include all of privGetJBMSLockOnDB as I think that will
still be required.
I found running the test with multiple threads that I would get occasional dual
boot without any error message or warning with the original patch. I expanded
the synchronization and found that it corrected the problem. I think there
seems to be a window where two threads can get in and create or delete the lock
file at the same time, e.g.
if (fileLock.exists())
{
...
----> Another thread gets in and deletes the file here
I am not totally sure that this is the hole and since this logic would remain
in BaseDataFileFactory we would still need to synchronize on the interned
databaseName there. I am sure however that it works with the expanded
synchronization but does not without 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: 10.1.2.1
> 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
> Assignee: Kathey Marsden
> Priority: Critical
> Fix For: 10.3.0.0
>
> Attachments: DERBY-700.diff, DERBY-700.stat,
> derby-700_06_07_07_diff.txt, derby-700_06_07_07_stat.txt, 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 [EMAIL PROTECTED]
> FAIL: Booted database in 2nd loader [EMAIL PROTECTED]
> 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 [EMAIL PROTECTED]
> PASS: Expected exception for dualboot:Another instance of Derby may have
> already booted the database D:\marsden\repro\dualboot\mydb.
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