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https://issues.apache.org/jira/browse/KAFKA-14225?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mickael Maison reassigned KAFKA-14225:
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Assignee: Huilin Shi
> lazy val exemptSensor Could Cause Deadlock
> ------------------------------------------
>
> Key: KAFKA-14225
> URL: https://issues.apache.org/jira/browse/KAFKA-14225
> Project: Kafka
> Issue Type: Bug
> Components: core
> Affects Versions: 2.5.1
> Reporter: Huilin Shi
> Assignee: Huilin Shi
> Priority: Blocker
> Fix For: 3.4.0, 3.3.2
>
>
> There is a chance to cause deadlock when multiple threads access
> ClientRequestQuotaManager.
> In the version of Scala 2.12, the lazy val initialization is under the object
> lock. The deadlock could happen in the following condition:
> In thread a, when ClientRequestQuotaManager.exemptSensor is being
> initialized, it has acquired the object lock and enters the the actual
> initialization block. The initialization of 'exemptSensor' requires another
> lock private val lock = new ReentrantReadWriteLock() and it is waiting for
> this lock.
> In thread b, at the same time, ClientQuotaManager.updateQuota() is called and
> it has already acquired ReentrantReadWriteLock lock by calling
> lock.writeLock().lock(). And then it executes info(). If this is the first
> time accessing Logging.logger, which is also a lazy val, it need to wait for
> the object lock.
> Deadlock happens.
> Since the lazy val initialization is under the object lock, we should avoid
> using lazy val if the initialization function holds another lock to prevent
> holding two locks at the same time which is prone for deadlock.
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