Issue
You upgraded to 1.609 through to 1.617, your instance doesn’t reply and a threads dump reports a deadlock where one of the deadlocks includes hudson.model.Queue.maintain() and the other deadlocked thread includes Executor like so:
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:186) at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:834) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:867) at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1197) at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:214) at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:290) at hudson.model.Queue._withLock(Queue.java:1205) at hudson.model.Queue.withLock(Queue.java:1143) at hudson.model.Computer.removeExecutor(Computer.java:977) at hudson.model.Executor.interrupt(Executor.java:187)
Resolution
This problem was reported as JENKINS-28840 and is fixed in Jenkins 1.618 (and should be in the LTS 1.609.3).
If you are running CloudBees Jenkins Enterprise 15.05 ( 1.609.1.1 ) please contact the CloudBees Support who will provide you a hotfix for this problem.