Classloading lock owned by a thread that hasn't appeared to sync on it blocking other threads from proceeding.

According to the thread dump 0x00000000e0463f10 is a
ReentrantLock$NonfairSync which two other threads are waiting to lock. It is
not clear from the thread dump which thread currently owns this lock, however
using kjdb & SA we see the following:

hsdb> inspect 0x00000000e0463f10
instance of Oop for java/util/concurrent/locks/ReentrantLock$NonfairSync @
0xe0463f10 @ 0xe0463f10 (size = 32)
_mark: 49
exclusiveOwnerThread: Oop for weblogic/work/ExecuteThread @ 0xe075e5b8 Oop
for weblogic/work/ExecuteThread @ 0xe075e5b8
head: Oop for java/util/concurrent/locks/AbstractQueuedSynchronizer$Node @
0xf869b810 Oop for java/util/concurrent/locks/AbstractQueuedSynchronizer$Node
0xf869b810
tail: Oop for java/util/concurrent/locks/AbstractQueuedSynchronizer$Node @
0xf88cf6f0 Oop for java/util/concurrent/locks/AbstractQueuedSynchronizer$Node
0xf88cf6f0
state: 1

inspect the owner thread:

hsdb> inspect 0xe075e5b8
instance of Oop for weblogic/work/ExecuteThread @ 0xe075e5b8 @ 0xe075e5b8
(size = 192)
_mark: 46912794892362
name: [C @ 0xe075e678 Oop for [C @ 0xe075e678
priority: 5
...
...
activeName: "[ACTIVE] ExecuteThread: '0' for queue: 'weblogic.kernel.Default
(self-tuning)'" @ 0xe07843c0 Oop for java/lang/String @ 0xe07843c0


x:c>threads | grep ExecuteThread


x:c>thread 0x6451
Thread: id = 0x6451 [ACTIVE] ExecuteThread: '0' for queue:
'weblogic.kernel.Default (self-tuning)' JavaThread
Oop=sun.jvm.hotspot.oops.Instance@e075e5b8 SP=0x4152f6a0 Stack: 0x4152f6a0 -
0x4152f9c0 used = 0x320(800b)

Thread nid=0x6451: (state = BLOCKED, current Java SP = 0x4152f8a0

 - java.lang.Object.wait(long) @bci=0, pc=0x2aaaab81bf67,
methodOop=0xd0002758 (Compiled frame; information may be imprecise)
 - java.lang.Object.wait() @bci=2, line=503, pc=0x2aaaab198058,
methodOop=0xd0002948 (Interpreted frame)
 - weblogic.work.ExecuteThread.waitForRequest() @bci=8, line=232,
pc=0x2aaaab198058, methodOop=0xd1b04c70 (Interpreted frame)
 - weblogic.work.ExecuteThread.run() @bci=120, line=266, pc=0x2aaaab87bf60,
methodOop=0xd1b04eb0 (Compiled frame)


This corresponds to the thread dump:

"[ACTIVE] ExecuteThread: '0' for queue: 'weblogic.kernel.Default
(self-tuning)'" daemon prio=10 tid=0x00002aaab495b800 nid=0x6451 in
Object.wait() [0x000000004152f000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:503)
        at weblogic.work.ExecuteThread.waitForRequest(ExecuteThread.java:232)
        - locked <0x00000000e075e5b8> (a weblogic.work.ExecuteThread)
        at weblogic.work.ExecuteThread.run(ExecuteThread.java:266)

It is not clear how this thread came to own the lock.