[logback-dev] About LBCORE-224...

[Holger Hoffstaette]

On Fri, 30 Sep 2011 18:36:54 +0200, Ceki Gülcü wrote:

> I don't see how anything a caller of logback, in this case zookeeper,
> could do to cause the readLock to be unlocked before it is locked.
> Actually, how could you trigger the observed behavior even if you wanted
> to trigger it on purpose? Do you have any ideas?

The most common cause seems to be a swallowed inner exception. Several
other findings seem to support this:

http://java.net/jira/browse/GLASSFISH-1881
http://lists.terracotta.org/pipermail/ehcache-list/2011-July/thread.html
http://cs.oswego.edu/pipermail/concurrency-interest/2006-June/002738.html

See last one for a good example.

Curiously it seems that this problem reared its head some time ago:
http://qos.ch/pipermail/logback-dev/2009-February/003620.html
though I think that was more about safe lock usage, which seems to be
addressed now.

Maybe somehow there _is_ a silent exception happening between
Logger.appendLoopOnAppenders() and AAI, since it also appears on the
JIRA's stack trace? I'm not familiar enough with logback's internals to
make more educated guesses right now.

The only thing I can immediately think of would be some weird recursive
logging from a threaded appender, with bits of StackOverflow (maybe
causing more logging..) thrown in.

-h