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https://issues.apache.org/jira/browse/GROOVY-8067?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15853145#comment-15853145
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ASF GitHub Bot commented on GROOVY-8067:
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GitHub user jwagenleitner opened a pull request:
https://github.com/apache/groovy/pull/489
GROOVY-8067: Possible deadlock when creating new ClassInfo entries in the
cache
As suggested in PR #484 removed the locking on the `ManagedLinkedList` by
creating a new `ManagedConcurrentLinkedQueue`.
Also added a `stress` subproject for tests that employ many threads, need
GC, or just in general try to break things and take a long time. These require
a special property to be set in order to run, otherwise they will be skipped.
I tried to work it out in the `performance` subproject, but that seems to be
very specialized for the compiler tests. Open to suggestions on a better way
to handle these types of tests.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/jwagenleitner/groovy groovy8067-mclq
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/groovy/pull/489.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #489
----
commit bb2464a919a3655f36707fa72fb30080c92a7288
Author: John Wagenleitner <[email protected]>
Date: 2017-02-05T06:13:26Z
GROOVY-8067: Possible deadlock when creating new ClassInfo entries in the
cache
----
> Possible deadlock when creating new ClassInfo entries in the cache
> ------------------------------------------------------------------
>
> Key: GROOVY-8067
> URL: https://issues.apache.org/jira/browse/GROOVY-8067
> Project: Groovy
> Issue Type: Bug
> Components: groovy-runtime
> Affects Versions: 2.4.8
> Reporter: John Wagenleitner
> Priority: Critical
> Attachments: ClassInfoDeadlockTest.java
>
>
> When running Groovy without {{-Dgroovy.use.classvalue=true}} the ClassInfo
> instances are cached in a {{ManagedConcurrentMap}} (MCM). New values are
> computed on demand and computation involves both a lock on a segment within
> the MCM and a lock on the {{GlobalClassSet}} (GCS) which is backed by a
> {{ManagedLinkedList}}. The problem is that both the ManagedConcurrentMap and
> the GlobalClassSet share the same ReferenceQueue.
> Assume there is an enqueued {{ClassInfo}} value that is stored in Segment2 of
> the MCM. Now assume that Thread1 and Thread2 both request
> {{ClassInfo.getClassInfo(..)}} for two different classes that do not
> currently exist in the cache. Assume that based on hashing Thread1 gets a
> lock on Segment1 and Thread2 gets a lock on Segment2. Assume that Thread1 is
> the first to call computeValue which in turn calls
> {{GlobalClassSet.add(..)}}. This call adds a new value to a
> {{ManagedLinkedList}}, and since it's managed the add operation will process
> the ReferenceQueue. So Thread1 will attempt to dequeue the ClassInfo and the
> finalizeReference method on it's entry will attempt to remove it from
> Segment2. Thread2 holds the lock for Segment2 and Thread2 is blocked and
> can't progress it's waiting on the the lock Thread1 holds the lock for the
> GlobalClassSet, so deadlock occurs.
> The attached test case includes a thread dump at the bottom.
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