[jira] [Created] (OAK-4972) Unprotected access to TAR readers and writer

["Francesco Mari (JIRA)" <ji...@apache.org>]

Francesco Mari created OAK-4972:
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             Summary: Unprotected access to TAR readers and writer
                 Key: OAK-4972
                 URL: https://issues.apache.org/jira/browse/OAK-4972
             Project: Jackrabbit Oak
          Issue Type: Bug
          Components: segment-tar
            Reporter: Francesco Mari
            Assignee: Francesco Mari
             Fix For: Segment Tar 0.0.18


The TAR readers and writers are sporadically accessed outside of the r/w lock that should protect them.

The TAR readers are accessed outside of the r/w lock in FileStore.containsSegment() and FileStore.readSegment(). This might introduce visibility issues - some threads might see stale data because of improper synchronization.

The TAR writer is accessed outside of the r/w lock in FileStore.flush(). Even if the access is protected by another lock (the flush lock), not using the same r/w lock to access the TAR writer in this context might introduce visibility issues.

Moreover, the r/w lock is sometimes used when accessing data other than the TAR readers and writer. This is the case of FileStore.close() accessing the file lock and of GarbageCollector.cleanup() accessing the segment cache and the segment tracker. This "protected" access might give a false sense of security, but is flaky and might introduce deadlocks if other locks are introduce in the future.



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