dead lock occur between Subscription and Subscriber

[wolfjiang]

Subscription.distributeMaxInFlight() lock itself with sync lock, and than access Subscriber.getLookupIntervalSecs() to get sync lock of Subscriber.

another thread Subscriber.lookup() lock itself with sync lock and than access Subscription.checkConnections() to get sync lock of Subscription.

the thread dump as follow:

"nsq-sub-0":
at com.sproutsocial.nsq.Subscriber.getLookupIntervalSecs(Subscriber.java:213)
- waiting to lock <0x00000003efa47af8> (a com.sproutsocial.nsq.Subscriber)
at com.sproutsocial.nsq.Subscription.distributeMaxInFlight(Subscription.java:76)
at com.sproutsocial.nsq.Subscription.setMaxInFlight(Subscription.java:38)
- locked <> 0x00000003efa47ff8(a com.sproutsocial.nsq.Subscription)
at com.sproutsocial.nsq.BackoffHandler.successDuringBackoff(BackoffHandler.java:103)
- locked <0x00000003efa480a0> (a com.sproutsocial.nsq.BackoffHandler)
at com.sproutsocial.nsq.BackoffHandler.accept(BackoffHandler.java:45)
at com.sproutsocial.nsq.SubConnection$3.run(SubConnection.java:178)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
"nsq-sched-1":
at com.sproutsocial.nsq.Subscription.checkConnections(Subscription.java:42)
- waiting to lock <0x00000003efa47ff8> (a com.sproutsocial.nsq.Subscription)
at com.sproutsocial.nsq.Subscriber.lookup(Subscriber.java:112)
- locked <0x00000003efa47af8> (a com.sproutsocial.nsq.Subscriber)
at com.sproutsocial.nsq.Subscriber.access$000(Subscriber.java:27)
at com.sproutsocial.nsq.Subscriber$1.run(Subscriber.java:51)
at com.sproutsocial.nsq.Client$1.run(Client.java:162)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)

subscriber.getLookupIntervalSecs() should not be synchronized?