QueryIteratorBase concurrency issues
------------------------------------
Key: JENA-100
URL: https://issues.apache.org/jira/browse/JENA-100
Project: Jena
Issue Type: Bug
Components: ARQ
Reporter: Stephen Allen
Attachments: JENA-100-r1157891.patch
QueryIteratorBase appears to have some concurrency bugs relating to cancelling
a query:
1) The cancel() and cancelAllowContinue() methods did not have large enough
synchronized blocks (they also used "this" as the lock, which is not
recommended)
2) The order of setting the cancellation flags and the notifying subclasses via
the requestCancel() method was incorrect
3) The visibility and happens-before relationships were incorrect for the
requestingCancel and abortIterator variables
The cancelAllowContinue() feature adds a lot of complexity in terms of
visibility and ordering. Unfortunately it is hard to write test cases for
these types of concurrency issues, so the existing tests did not uncover the
issues.
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira
