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https://issues.apache.org/jira/browse/HIVE-16433?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15968060#comment-15968060
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Jimmy Xiang commented on HIVE-16433:
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Ok, thanks for the explanation. +1

> Not nullify variable "rj" to avoid NPE due to race condition in ExecDriver.
> ---------------------------------------------------------------------------
>
>                 Key: HIVE-16433
>                 URL: https://issues.apache.org/jira/browse/HIVE-16433
>             Project: Hive
>          Issue Type: Bug
>            Reporter: zhihai xu
>            Assignee: zhihai xu
>            Priority: Minor
>         Attachments: HIVE-16433.000.patch
>
>
> Not nullify variable {{rj}} to avoid NPE due to race condition in ExecDriver. 
> currently  {{rj}} is set to null in ExecDriver.shutdown which is called from 
> other thread for query cancellation. It can happen at any time. There is a 
> potential race condition,  the {{rj}} is still accessed after shutdown is 
> called. For example: if the following code is executed right after 
> ExecDriver.shutdown is called.
> {code}
>       this.jobID = rj.getJobID();
>       updateStatusInQueryDisplay();
>       returnVal = jobExecHelper.progress(rj, jc, ctx);
> {code}
> Currently the purpose of nullifying  {{rj}} is mainly to make sure 
> {{rj.killJob()}} is only called once.
> I will add a flag {{jobKilled}} to make sure {{rj.killJob()}} will be only 
> called once.



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