hi all,
there are a number of synchronization issues I would like to resolve for the 1.4
release. some of them are related to using the new FineGrainedISMLocking but
most of them are general synchronization issues that may happen with both
DefaultISMLocking and FineGrainedISMLocking, though more visible with the latter.
JCR-1271 - this issue happens with both ISMLocking implementations. The cache in
LocalItemStateManager is accessed at the same time by the thread using the
session and by the thread that notifies ItemState changes. JCR-935 happens for
the same reason.
JCR-1272 - this issue happens with both ISMLocking implementations. instead of
adding synchronization, I suggest to operate on possibly stale states. see patch.
JCR-1274 - this is only an issue with the FineGrainedISMLocking. when using the
DefaultISMLocking the exclusive write lock prevents any reading from the cache.
this is different when using FineGrainedISMLocking. This locking strategy allows
reading from the cache while a change is processed. Hence it may happen that
reading from and writing to the cache happens concurrently. One solution may be
to completely synchronize the ItemStateCache in SharedItemStateManager. This
however reduces concurrency on the cache for reading threads. Another solution I
can think of is to allow the ISMLocking implementation to wrap the
ItemStateCache if necessary. DefaultISMLocking would simply return the cache as
is, while FineGrainedISMLocking would have to wrap the cache into a synchronized
variant.
comments are welcome.
regards
marcel
