Hello, I tried to build all modules under xwiki-platform-core, but the build process hanged on PreemtiveLockTest, so I had a look at the code and noticed some problems:
1. PreemtiveLockProvider.lockBlockingThread is concurrently accessed and updated despite being an unsynchronized HashMap. It must be synchronized. 2. The deadlock recovery algorithm is "if there is a deadlock, ignore the fact that the lock is locked and proceed." To me this seems unintuitive. When a deadlock is detected, an exception should be thrown and the thread aborted. 3. Presumably, the thread which is deprived of its lock is supposed to at least be blocked until the thieving thread unlocks the lock, but there is a race condition so both threads may run simultaneously. 4. Related to 3., the 'owners' stack in the lock is concurrently accessed without synchronization in 'currentThreadOwnsAllLocks'. As of deadlock detection, do we really need it? If so, would java.lang.management.ThreadMXBean.findDeadlockedThreads() be sufficient? In my opinion, the implementation PreemtiveLock should be discarded and the LockProvider should return an ordinary ReentrantReadWriteLock. Best Regards, /Andreas _______________________________________________ devs mailing list [email protected] http://lists.xwiki.org/mailman/listinfo/devs
