FlowController.incrementRequestCount() and
FlowController.decrementRequestCount() access the variables
_requestCount and _maxConcurrentRequestCount outside of any synchronized
block. This makes it possible to _requestCount, especially on a
multi-processor machine. The subtlety of this bug is that
--_requestCount and ++_requestCount look atomic, but they are not.
In particular, we have an action that returns images. Since some pages
contain many images, this controller can be hit my many requests
concurrently from the same session. We hit the decrementRequestCount()
assert quite frequently in production.
assert _requestCount > 0 : request.getRequestURI();
Thanks,
Matt
