Interrupting a thread, which is currently performing I/O on Lucene index files, may result in closed index files. Jackrabbit versions prior to 2.4 didn't have that problem because only with the update of Lucene to 3.0.3 in Jackrabbit 2.4 the underlying default for the FSDirectory in Lucene changed from SimpleFSDirectory to NIOFSDirectory. The latter uses a FileChannel to perform concurrent read operations on a single channel, but because of the way how FileChannel is specified an interrupt will result in the FileChannel to be closed.
This was also discussed on the Lucene mailing list. See: http://lucene.markmail.org/thread/ea7mj2kpdvyuesss