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Posted to oak-issues@jackrabbit.apache.org by "Michael Dürig (JIRA)" <ji...@apache.org> on 2016/09/19 16:13:20 UTC

[jira] [Created] (OAK-4824) Deadlock in TarWriter

Michael Dürig created OAK-4824:
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             Summary: Deadlock in TarWriter
                 Key: OAK-4824
                 URL: https://issues.apache.org/jira/browse/OAK-4824
             Project: Jackrabbit Oak
          Issue Type: Bug
          Components: segment-tar
            Reporter: Michael Dürig
            Priority: Critical
             Fix For: Segment Tar 0.0.14


There is the potential for a deadlock between concurrent calls to {{TarWriter#createNextGeneration()}} and {{TarWriter#flush()}}: both methods try to acquire a lock on this and another lock on {{TarWriter.file}} but in different order. I observed the deadlock when running {{CompactionAndCleanupIT.randomAccessFileConcurrentReadAndLength()}}.

This is a regression introduced with OAK-4746: the method {{TarWriter.createNextGeneration()}} seems over eagerly synchronized. I would argue that we could drop synchronization for that method entirely as the part after the call to {{close()}} will in any case only ever be executed once by a single thread. All other threads will fail with an {{IllegalStateException}}).

[~alexparvulescu], WDYT?



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