Hi, I'm currently building ActiveMQ using Java 25, and running into some problems where running tests will just 'lock up'. An example is JmsSchedulerTest. These two threads are both blocked:
"main" #3 [5635] prio=5 os_prio=31 cpu=657.39ms elapsed=1429.54s tid=0x000000013401ee00 nid=5635 waiting on condition [0x000000016bacd000] java.lang.Thread.State: WAITING (parking) at jdk.internal.misc.Unsafe.park(java.base@25/Native Method) - parking to wait for <0x00000007e0cdd530> (a java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync) at java.util.concurrent.locks.LockSupport.park(java.base@25 /LockSupport.java:223) at java.util.concurrent.locks.AbstractQueuedLongSynchronizer.acquire(java.base@25 /AbstractQueuedLongSynchronizer.java:410) at java.util.concurrent.locks.AbstractQueuedLongSynchronizer.acquire(java.base@25 /AbstractQueuedLongSynchronizer.java:650) at java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(java.base@25 /ReentrantReadWriteLock.java:966) at org.apache.activemq.store.kahadb.scheduler.JobSchedulerStoreImpl.unload(JobSchedulerStoreImpl.java:214) at org.apache.activemq.store.kahadb.AbstractKahaDBStore.doStop(AbstractKahaDBStore.java:141) at org.apache.activemq.util.ServiceSupport.stop(ServiceSupport.java:71) at org.apache.activemq.broker.scheduler.SchedulerBroker.stop(SchedulerBroker.java:223) at org.apache.activemq.broker.BrokerFilter.stop(BrokerFilter.java:194) at org.apache.activemq.broker.TransactionBroker.stop(TransactionBroker.java:209) at org.apache.activemq.broker.BrokerService$3.stop(BrokerService.java:2363) at org.apache.activemq.util.ServiceStopper.stop(ServiceStopper.java:41) at org.apache.activemq.broker.BrokerService.stop(BrokerService.java:849) at org.apache.activemq.broker.scheduler.JobSchedulerTestSupport.tearDown(JobSchedulerTestSupport.java:69) at java.lang.invoke.LambdaForm$DMH/0x000001ff01108000.invokeVirtual(java.base@25 /LambdaForm$DMH) at java.lang.invoke.LambdaForm$MH/0x000001ff01108800.invoke(java.base@25 /LambdaForm$MH) at java.lang.invoke.Invokers$Holder.invokeExact_MT(java.base@25 /Invokers$Holder) at jdk.internal.reflect.DirectMethodHandleAccessor.invokeImpl(java.base@25 /DirectMethodHandleAccessor.java:154) at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(java.base@25 /DirectMethodHandleAccessor.java:104) at java.lang.reflect.Method.invoke(java.base@25/Method.java:565) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56) at org.junit.internal.runners.statements.RunAfters.invokeMethod(RunAfters.java:46) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:33) at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:61) at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63) at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329) at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293) at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306) at org.junit.runners.ParentRunner.run(ParentRunner.java:413) at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:316) at org.apache.maven.surefire.junit4.JUnit4Provider.executeWithRerun(JUnit4Provider.java:240) at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:214) at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:155) at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:385) at org.apache.maven.surefire.booter.ForkedBooter.execute(ForkedBooter.java:162) at org.apache.maven.surefire.booter.ForkedBooter.run(ForkedBooter.java:507) at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:495) "JobScheduler:JMS" #129 [42779] daemon prio=5 os_prio=31 cpu=10.67ms elapsed=1417.10s tid=0x000000013200c000 nid=42779 waiting on condition [0x0000000328c42000] java.lang.Thread.State: WAITING (parking) at jdk.internal.misc.Unsafe.park(java.base@25/Native Method) - parking to wait for <0x00000007e0cdd530> (a java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync) at java.util.concurrent.locks.LockSupport.park(java.base@25 /LockSupport.java:223) at java.util.concurrent.locks.AbstractQueuedLongSynchronizer.acquire(java.base@25 /AbstractQueuedLongSynchronizer.java:410) at java.util.concurrent.locks.AbstractQueuedLongSynchronizer.acquire(java.base@25 /AbstractQueuedLongSynchronizer.java:650) at java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(java.base@25 /ReentrantReadWriteLock.java:966) at org.apache.activemq.store.kahadb.scheduler.JobSchedulerStoreImpl$8.visit(JobSchedulerStoreImpl.java:696) at org.apache.activemq.store.kahadb.data.KahaAddScheduledJobCommand.visit(KahaAddScheduledJobCommand.java:283) at org.apache.activemq.store.kahadb.scheduler.JobSchedulerStoreImpl.process(JobSchedulerStoreImpl.java:691) at org.apache.activemq.store.kahadb.AbstractKahaDBStore.store(AbstractKahaDBStore.java:495) at org.apache.activemq.store.kahadb.AbstractKahaDBStore.store(AbstractKahaDBStore.java:403) at org.apache.activemq.store.kahadb.scheduler.JobSchedulerImpl.doSchedule(JobSchedulerImpl.java:252) at org.apache.activemq.store.kahadb.scheduler.JobSchedulerImpl.schedule(JobSchedulerImpl.java:100) at org.apache.activemq.store.kahadb.scheduler.JobSchedulerImpl.mainLoop(JobSchedulerImpl.java:782) at org.apache.activemq.store.kahadb.scheduler.JobSchedulerImpl.run(JobSchedulerImpl.java:699) at java.lang.Thread.runWith(java.base@25/Thread.java:1487) at java.lang.Thread.run(java.base@25/Thread.java:1474) Looking at the ReentrantReadWriteLock$NonfairSync in question in a heap dump, the 'firstReader' is the JobScheduler:JMS thread, which I assume has a read lock on this already and both threads are attempting to acquire a write lock. Weirdly, I don't see this with Java 21. I'll try and dig in to get some more information on what's happening, and if appropriate, send a patch. Any thoughts are welcome - and if no-one has any thoughts, that's cool too, I'm happy to continue working through this and report back. Jon
