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From "Andrew Chung (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (REEF-1403) Deadlock between ContextRuntime.StartTask and HeartBeatManager.OnNext(Alarm)
Date Thu, 26 May 2016 16:32:13 GMT

    [ https://issues.apache.org/jira/browse/REEF-1403?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15302356#comment-15302356
] 

Andrew Chung commented on REEF-1403:
------------------------------------

It would appear that all the control flow goes through {{EvaluatorRuntime}}, and while we
were locking on {{HeartbeatManager}} on all {{EvaluatorControlProto}} messages, we were not
locking on {{HeartbeatManager}} in {{OnNext(RuntimeStart)}}. This should be why this deadlock
is only triggered on the starting of an Evaluator, otherwise it should occur much more frequently.

> Deadlock between ContextRuntime.StartTask and HeartBeatManager.OnNext(Alarm)
> ----------------------------------------------------------------------------
>
>                 Key: REEF-1403
>                 URL: https://issues.apache.org/jira/browse/REEF-1403
>             Project: REEF
>          Issue Type: Bug
>          Components: REEF.NET Evaluator
>            Reporter: Mariia Mykhailova
>
> We have a potential deadlock in task start/timed heartbeats.
> {{ContextRuntime.StartTask}} does the following:
> 1. Acquires lock on {{ContextRuntime._contextLifeCycle}}
> 2. Calls {{TaskRuntime.RunTask()}} which calls {{TaskStatus.setInit}} which calls {{HeartBeatManager.onNext(TaskStatusProto)}}
which acquires lock on {{HeartBeatManager}} itself.
> At the same time {{HeartBeatManager.onNext(Alarm)}} gets called every 4 seconds since
evaluator start, and it:
> 1. Acquires lock on {{HeartBeatManager}}.
> 2. Calls {{GetEvaluatorHeartbeatProto}} which calls {{ContextManager.GetTaskStatus()}}
which calls {{ContextManager.GetTaskStatus()}} which acquires lock on {{ContextRuntime._contextLifeCycle}}.
> If task will be starting at the same time as heartbeat kick in, these two actions will
deadlock each other. I encountered a repro on our tests when working on REEF-1388, but in
general case it's not impossible that second or third task that starts on evaluator runs into
a heartbeat.



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