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https://issues.apache.org/jira/browse/DERBY-4928?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kristian Waagan updated DERBY-4928:
-----------------------------------
Attachment: derby-4928-1a-depman_sync_and_cleanup.diff
Attaching patch 1a.
This patch primarily addresses incorrect synchronization in
BasicDependencyManager. The rule was already described in the class, but the
implementation didn't obey them:
o use synchronized (this) when accessing in-memory dependencies (deps stored
in BasicDependencyManager)
o don't use synchronized (this) when accessing stored dependencies, but rely
on database locking (deps stored in the data dictionary / a system table)
I haven't come across cases where we need to synchronize over both sets of
dependencies (at the same time).
Main changes in BasicDependecyManager:
o split body of addDepencendy into addInMemoryDependency and
addStoredDependency
o corrected JavaDoc for coreInvalidateFor (the flag 'forSync' doesn't exist)
o fixed synchronization in clearDependencies (this is where the automatic
index stats update feature got stuck in a deadlock)
o reformatted (+tiny refactoring) clearInMemoryDependencies
o deleted commented out methods getAllProviders and getAllProvidersInfos
o removed synchronized for getPersistentProvidersInfos and rewrote method
o removed synchronized for copyDependencies
o fixed synchronization in countDependencies
o deleted unused method dumpDependencies (and then bubbleSort)
o rewrote methods getProviders and getDependents for new sync rules
o replaced HashTable with Map
o removed methods newSList
Changes in ViewsTest and BaseJDBCTestCase:
o added method assertStatementErrorUnordered, as the ordering of in-memory and
stored dependencies changed to to the changes described above (this can easily
be switched back, but I don't see why - decided to make the test more resilient
to varying ordering instead).
o used the new assert method were the test failed
Re-running regression tests.
Patch ready for review.
> Deadlock-prone synchronization in BasicDependencyManager
> --------------------------------------------------------
>
> Key: DERBY-4928
> URL: https://issues.apache.org/jira/browse/DERBY-4928
> Project: Derby
> Issue Type: Bug
> Components: SQL
> Affects Versions: 10.8.0.0
> Reporter: Kristian Waagan
> Assignee: Kristian Waagan
> Attachments: derby-4928-1a-depman_sync_and_cleanup.diff
>
>
> The synchronization in BasicDependencyManager is prone to deadlock, because
> database locks are obtained while holding the monitor on "this".
> Problem observed when testing the automatic index statistics update prototype.
> There are comments in the file suggesting that in-memory dependencies should
> be accessed while holding the Java monitor, but the monitor should not be
> held when accessing stored dependencies. The implementation is breaking this
> rule/suggestion.
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