Hmm, thought the new parallel lock stategy in ClassLoader wasn't
deadlock prone? Guess I was wrong.
Observation: On an unrelated occassion, I had a URLClassLoader
synchronization hotspot (well not standard URLClassLoader, but a high
performance RFC3986 URL ClassLoader, that use normalized RFC3986 URI
instead of URL DNS lookup), I solved that problem by thread confining
class loading. I've never experienced deadlock using thread
confinement, initially I was worried that there would be
interdependencies, however I didn't experience a problem, as the single
thread would always load the classes it needed.
I'm wondering if multiple locks for ClassLoader's might be the wrong
strategy, I found thread confinement was very performant.
Regards,
Peter.
2016-02-06 21:06:07
Full thread dump Java HotSpot(TM) Client VM (25.0-b70 mixed mode):
"Service Thread" #9 daemon prio=9 os_prio=0 tid=0x14387400 nid=0xc54
runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
"C1 CompilerThread0" #8 daemon prio=9 os_prio=2 tid=0x14332c00
nid=0x111c waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
"Attach Listener" #7 daemon prio=5 os_prio=2 tid=0x14331c00 nid=0x13d8
waiting on condition [0x00000000]
java.lang.Thread.State: RUNNABLE
"Signal Dispatcher" #6 daemon prio=9 os_prio=2 tid=0x14331400 nid=0x10b8
runnable [0x00000000]
java.lang.Thread.State: RUNNABLE
"Thread-1" #5 prio=10 os_prio=2 tid=0x14318800 nid=0x4a8 waiting for
monitor entry [0x03ded000]
java.lang.Thread.State: BLOCKED (on object monitor)
at
org.apache.river.concurrent.ReferenceCollection.iterator(ReferenceCollection.java:124)
at
org.apache.river.concurrent.ReferenceSet.hashCode(ReferenceSet.java:65)
at
org.apache.river.concurrent.StrongReference.<init>(StrongReference.java:44)
at
org.apache.river.concurrent.StrongReference.<init>(StrongReference.java:57)
at
org.apache.river.concurrent.ReferenceFactory.create(ReferenceFactory.java:64)
at
org.apache.river.concurrent.ReferenceProcessor.referenced(ReferenceProcessor.java:128)
at
org.apache.river.concurrent.ReferenceProcessor.referenced(ReferenceProcessor.java:44)
at
org.apache.river.concurrent.ReferenceMap.wrapVal(ReferenceMap.java:244)
at
org.apache.river.concurrent.ReferenceConcurrentMap.putIfAbsent(ReferenceConcurrentMap.java:68)
at
org.apache.river.api.security.CombinerSecurityManager.checkPermission(CombinerSecurityManager.java:261)
at
org.apache.river.api.security.CombinerSecurityManager.checkPermission(CombinerSecurityManager.java:202)
at
java.net.NetworkInterface.getHardwareAddress(NetworkInterface.java:447)
at
java.util.concurrent.ThreadLocalRandom.initialSeed(ThreadLocalRandom.java:158)
at
java.util.concurrent.ThreadLocalRandom.<clinit>(ThreadLocalRandom.java:137)
at
java.util.concurrent.ConcurrentHashMap.fullAddCount(ConcurrentHashMap.java:2526)
at
java.util.concurrent.ConcurrentHashMap.addCount(ConcurrentHashMap.java:2266)
at
java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1070)
at
java.util.concurrent.ConcurrentHashMap.putIfAbsent(ConcurrentHashMap.java:1535)
at java.lang.ClassLoader.getClassLoadingLock(ClassLoader.java:463)
at java.lang.ClassLoader.loadClass(ClassLoader.java:404)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
- locked <0x03f624b8> (a java.lang.Object)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at
org.cliffc.high_scale_lib.NonBlockingHashMap$SnapshotK.<init>(NonBlockingHashMap.java:1167)
at
org.cliffc.high_scale_lib.NonBlockingHashMap$2.iterator(NonBlockingHashMap.java:1200)
at
org.apache.river.concurrent.ReferenceProcessor$EnqueGarbageTask.run(ReferenceProcessor.java:166)
- locked <0x03ef8b30> (a
org.cliffc.high_scale_lib.NonBlockingHashMap)
at
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.j
ava:180)
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294
)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:744)
"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x14277800 nid=0x15cc in
Object.wait() [0x03cff000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x03e056d8> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:142)
- locked <0x03e056d8> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:158)
at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)
"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x14271c00
nid=0x1398 in Object.wait() [0x144cf000]
java.lang.Thread.State: WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
- waiting on <0x03e05200> (a java.lang.ref.Reference$Lock)
at java.lang.Object.wait(Object.java:502)
at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:157)
- locked <0x03e05200> (a java.lang.ref.Reference$Lock)
"main" #1 prio=5 os_prio=0 tid=0x017cf400 nid=0x1284 waiting for monitor
entry [0x0185e000]
java.lang.Thread.State: BLOCKED (on object monitor)
at java.lang.ClassLoader.loadClass(ClassLoader.java:406)
- waiting to lock <0x03f624b8> (a java.lang.Object)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at
org.apache.river.concurrent.ReferenceCollection.iterator(ReferenceCollection.java:124)
at
org.apache.river.concurrent.ReferenceSet.hashCode(ReferenceSet.java:65)
at
org.apache.river.concurrent.StrongReference.<init>(StrongReference.java:44)
at
org.apache.river.concurrent.StrongReference.<init>(StrongReference.java:57)
at
org.apache.river.concurrent.ReferenceFactory.create(ReferenceFactory.java:64)
at
org.apache.river.concurrent.ReferenceProcessor.referenced(ReferenceProcessor.java:128)
at
org.apache.river.concurrent.ReferenceProcessor.referenced(ReferenceProcessor.java:44)
at
org.apache.river.concurrent.ReferenceMap.wrapVal(ReferenceMap.java:244)
at
org.apache.river.concurrent.ReferenceConcurrentMap.putIfAbsent(ReferenceConcurrentMap.java:68)
at
org.apache.river.api.security.CombinerSecurityManager.checkPermission(CombinerSecurityManager.java:261)
at
org.apache.river.api.security.CombinerSecurityManager.checkPermission(CombinerSecurityManager.java:202)
at java.lang.System.checkIO(System.java:253)
at java.lang.System.setErr(System.java:199)
at org.apache.river.qa.harness.MasterTest.main(MasterTest.java:84)
"VM Thread" os_prio=2 tid=0x1426e400 nid=0x16a8 runnable
"VM Periodic Task Thread" os_prio=2 tid=0x14388400 nid=0x17a8 waiting on
condition
JNI global references: 19
Found one Java-level deadlock:
=============================
"Thread-1":
waiting to lock monitor 0x142766ac (object 0x040ebee8, a [I),
which is held by "main"
"main":
waiting to lock monitor 0x14274a3c (object 0x03f624b8, a
java.lang.Object),
which is held by "Thread-1"
Java stack information for the threads listed above:
===================================================
"Thread-1":
at
org.apache.river.concurrent.ReferenceCollection.iterator(ReferenceCollection.java:124)
at
org.apache.river.concurrent.ReferenceSet.hashCode(ReferenceSet.java:65)
at
org.apache.river.concurrent.StrongReference.<init>(StrongReference.java:44)
at
org.apache.river.concurrent.StrongReference.<init>(StrongReference.java:57)
at
org.apache.river.concurrent.ReferenceFactory.create(ReferenceFactory.java:64)
at
org.apache.river.concurrent.ReferenceProcessor.referenced(ReferenceProcessor.java:128)
at
org.apache.river.concurrent.ReferenceProcessor.referenced(ReferenceProcessor.java:44)
at
org.apache.river.concurrent.ReferenceMap.wrapVal(ReferenceMap.java:244)
at
org.apache.river.concurrent.ReferenceConcurrentMap.putIfAbsent(ReferenceConcurrentMap.java:68)
at
org.apache.river.api.security.CombinerSecurityManager.checkPermission(CombinerSecurityManager.java:261)
at
org.apache.river.api.security.CombinerSecurityManager.checkPermission(CombinerSecurityManager.java:202)
at
java.net.NetworkInterface.getHardwareAddress(NetworkInterface.java:447)
at
java.util.concurrent.ThreadLocalRandom.initialSeed(ThreadLocalRandom.java:158)
at
java.util.concurrent.ThreadLocalRandom.<clinit>(ThreadLocalRandom.java:137)
at
java.util.concurrent.ConcurrentHashMap.fullAddCount(ConcurrentHashMap.java:2526)
at
java.util.concurrent.ConcurrentHashMap.addCount(ConcurrentHashMap.java:2266)
at
java.util.concurrent.ConcurrentHashMap.putVal(ConcurrentHashMap.java:1070)
at
java.util.concurrent.ConcurrentHashMap.putIfAbsent(ConcurrentHashMap.java:1535)
at java.lang.ClassLoader.getClassLoadingLock(ClassLoader.java:463)
at java.lang.ClassLoader.loadClass(ClassLoader.java:404)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
- locked <0x03f624b8> (a java.lang.Object)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at
org.cliffc.high_scale_lib.NonBlockingHashMap$SnapshotK.<init>(NonBlockingHashMap.java:1167)
at
org.cliffc.high_scale_lib.NonBlockingHashMap$2.iterator(NonBlockingHashMap.java:1200)
at
org.apache.river.concurrent.ReferenceProcessor$EnqueGarbageTask.run(ReferenceProcessor.java:166)
- locked <0x03ef8b30> (a
org.cliffc.high_scale_lib.NonBlockingHashMap)
at
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.j
ava:180)
at
java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294
)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:744)
"main":
at java.lang.ClassLoader.loadClass(ClassLoader.java:406)
- waiting to lock <0x03f624b8> (a java.lang.Object)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at
org.apache.river.concurrent.ReferenceCollection.iterator(ReferenceCollection.java:124)
at
org.apache.river.concurrent.ReferenceSet.hashCode(ReferenceSet.java:65)
at
org.apache.river.concurrent.StrongReference.<init>(StrongReference.java:44)
at
org.apache.river.concurrent.StrongReference.<init>(StrongReference.java:57)
at
org.apache.river.concurrent.ReferenceFactory.create(ReferenceFactory.java:64)
at
org.apache.river.concurrent.ReferenceProcessor.referenced(ReferenceProcessor.java:128)
at
org.apache.river.concurrent.ReferenceProcessor.referenced(ReferenceProcessor.java:44)
at
org.apache.river.concurrent.ReferenceMap.wrapVal(ReferenceMap.java:244)
at
org.apache.river.concurrent.ReferenceConcurrentMap.putIfAbsent(ReferenceConcurrentMap.java:68)
at
org.apache.river.api.security.CombinerSecurityManager.checkPermission(CombinerSecurityManager.java:261)
at
org.apache.river.api.security.CombinerSecurityManager.checkPermission(CombinerSecurityManager.java:202)
at java.lang.System.checkIO(System.java:253)
at java.lang.System.setErr(System.java:199)
at org.apache.river.qa.harness.MasterTest.main(MasterTest.java:84)
Found 1 deadlock.
