Prevent endless loop in lock cycle detection #1510

This change prevents an endless loop in:
ReentrantCycleDetectingLock.addAllLockIdsAfter()

For reasons that are not yet clear, according to
CycleDetectingLockFactory.locksOwnedByThread and
ReentrantCycleDetectingLock.lockOwnerThread, a thread both owns a lock
and waits on that same lock. This leads to an endless loop in the cycle
detection.

The change adds a workaround, forcing the cycle detection to exit if the
above condition is met.

core/src/com/google/inject/internal/CycleDetectingLock.java

@@ -255,6 +255,7 @@ private ListMultimap<Thread, ID> detectPotentialLocksCycle() {
           // in case locks cycle exists lock we're waiting for is part of it
           lockOwnerWaitingOn =
               addAllLockIdsAfter(threadOwnerThreadWaits, lockOwnerWaitingOn, potentialLocksCycle);
+
           if (threadOwnerThreadWaits == currentThread) {
             // owner thread depends on current thread, cycle detected
             return potentialLocksCycle;
@@ -293,6 +294,10 @@ private ReentrantCycleDetectingLock<?> addAllLockIdsAfter(
         Preconditions.checkState(
             found, "Internal error: We can not find locks that created a cycle that we detected");
         ReentrantCycleDetectingLock<?> unownedLock = lockThreadIsWaitingOn.get(thread);
+        if (unownedLock == lock) {
+          // XXX: bandaid, how do we have a thread that owns a lock but also waits on that same lock?
+          return null;
+        }
         // If this thread is waiting for a lock add it to the cycle and return it
         if (unownedLock != null && unownedLock.lockFactory == this.lockFactory) {
           @SuppressWarnings("unchecked")