Jean-Louis Monteiro created AMQ-9808:
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Summary: Dead lock when using CRON schedule with
AMQ_SCHEDULED_REPEAT
Key: AMQ-9808
URL: https://issues.apache.org/jira/browse/AMQ-9808
Project: ActiveMQ Classic
Issue Type: Bug
Components: Job Scheduler
Affects Versions: 6.1.8, 5.18.7, 5.19.1
Reporter: Jean-Louis Monteiro
This bug is highlighted by the current JmsSchedulerTest@testCron() test case.
When using a CRON expression with repeat != 0, there is a deadlock happening
between JobSchedulerImpl and JobSchedulerStoreImpl.
The original cron job is read inside JobSchedulerImpl.mainLoop(). That loop
holds JobSchedulerStoreImpl.readLockIndex() for the whole iteration.
When it hits the cron branch with repeat != 0, the code tries to spawn a new
(non-cron) schedule by calling schedule(jobId, payload, "", delay, period,
repeat) while the read lock is still held. schedule() writes a new
KahaAddScheduledJobCommand, and JobSchedulerStoreImpl.process() needs the same
indexLock in write mode. Since the scheduler thread already holds the read
lock, it can’t acquire the write lock and blocks forever.
{code:java}
"JobScheduler:JMS" #46 [38147] daemon prio=5 os_prio=31 cpu=3.54ms
elapsed=273.52s tid=0x0000000ac8330800 nid=38147 waiting on condition
[0x0000000171df6000]
java.lang.Thread.State: WAITING (parking)
at jdk.internal.misc.Unsafe.park([email protected]/Native Method)
- parking to wait for <0x0000000343ac3e80> (a
java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
at
java.util.concurrent.locks.LockSupport.park([email protected]/LockSupport.java:223)
at
java.util.concurrent.locks.AbstractQueuedLongSynchronizer.acquire([email protected]/AbstractQueuedLongSynchronizer.java:410)
at
java.util.concurrent.locks.AbstractQueuedLongSynchronizer.acquire([email protected]/AbstractQueuedLongSynchronizer.java:650)
at
java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock([email protected]/ReentrantReadWriteLock.java:966)
at
org.apache.activemq.store.kahadb.scheduler.JobSchedulerStoreImpl$8.visit(JobSchedulerStoreImpl.java:684)
at
org.apache.activemq.store.kahadb.data.KahaAddScheduledJobCommand.visit(KahaAddScheduledJobCommand.java:283)
at
org.apache.activemq.store.kahadb.scheduler.JobSchedulerStoreImpl.process(JobSchedulerStoreImpl.java:679)
at
org.apache.activemq.store.kahadb.AbstractKahaDBStore.store(AbstractKahaDBStore.java:495)
at
org.apache.activemq.store.kahadb.AbstractKahaDBStore.store(AbstractKahaDBStore.java:403)
at
org.apache.activemq.store.kahadb.scheduler.JobSchedulerImpl.doSchedule(JobSchedulerImpl.java:252)
at
org.apache.activemq.store.kahadb.scheduler.JobSchedulerImpl.schedule(JobSchedulerImpl.java:100)
at
org.apache.activemq.store.kahadb.scheduler.JobSchedulerImpl.mainLoop(JobSchedulerImpl.java:782)
at
org.apache.activemq.store.kahadb.scheduler.JobSchedulerImpl.run(JobSchedulerImpl.java:699)
at java.lang.Thread.runWith([email protected]/Thread.java:1487)
at java.lang.Thread.run([email protected]/Thread.java:1474)
"ActiveMQ Journal Checkpoint Worker" #43 [38915] daemon prio=5 os_prio=31
cpu=4.77ms elapsed=273.69s tid=0x0000000ac82f5000 nid=38915 waiting on
condition [0x00000001719de000]
java.lang.Thread.State: WAITING (parking)
at jdk.internal.misc.Unsafe.park([email protected]/Native Method)
- parking to wait for <0x0000000343ac3e80> (a
java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
at
java.util.concurrent.locks.LockSupport.park([email protected]/LockSupport.java:223)
at
java.util.concurrent.locks.AbstractQueuedLongSynchronizer.acquire([email protected]/AbstractQueuedLongSynchronizer.java:410)
at
java.util.concurrent.locks.AbstractQueuedLongSynchronizer.acquire([email protected]/AbstractQueuedLongSynchronizer.java:650)
at
java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock([email protected]/ReentrantReadWriteLock.java:966)
at
org.apache.activemq.store.kahadb.AbstractKahaDBStore.checkpointCleanup(AbstractKahaDBStore.java:739)
at
org.apache.activemq.store.kahadb.AbstractKahaDBStore$2.run(AbstractKahaDBStore.java:707)
{code}
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