RFR: 8148507: [JVMCI] mitigate deadlocks related to JVMCI compiler under -Xbatch

[Tom Rodriguez]

>> 2. wait_for_jvmci_completion can still fail to return for arbitrarily long periods of time if compilation progresses but at a very slow rate.
> 
> Yes, that’s unfortunately unavoidable. But as mentioned elsewhere, -Xbatch is a "best effort” VM option.

I don’t think it can be arbitrarily long.  There can only be as many blocking compiles pending as there are running Java threads and the JVMCI compilation policy prioritizes blocking compiles over non-blocking ones so you shouldn’t end up waiting arbitrarily long.  Compiles triggered by the JVMCI compiler itself are never blocking so those will always be serviced last in this mode.  

tom

> 
> Thanks for the review.
> 
> -Doug
> 
>>>> On Feb 4, 2016, at 12:36 PM, Doug Simon <doug.simon at oracle.com> wrote:
>>>> 
>>>> I’ve updated the webrev in situ for reasons discussed here:
>>>> 
>>>> https://bugs.openjdk.java.net/browse/JDK-8148507?focusedCommentId=13896252&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13896252
>>>> 
>>>> 
>>>>> On 03 Feb 2016, at 20:42, Christian Thalinger <christian.thalinger at oracle.com> wrote:
>>>>> 
>>>>> There was some discussion in the bug report but I seems like we are going to integrate this change.
>>>>> 
>>>>>> On Jan 31, 2016, at 5:48 AM, Christian Thalinger <christian.thalinger at oracle.com> wrote:
>>>>>> 
>>>>>> Looks good.
>>>>>> 
>>>>>>> On Jan 29, 2016, at 4:34 PM, Doug Simon <doug.simon at oracle.com> wrote:
>>>>>>> 
>>>>>>> Please review this small change to further mitigate deadlocks that can be caused by JVMCI when BackgroundCompilation is disabled.
>>>>>>> 
>>>>>>> https://bugs.openjdk.java.net/browse/JDK-8148507
>>>>>>> http://cr.openjdk.java.net/~dnsimon/8148507
>>>>>>> 
>>>>>>> -Doug
>>>>>> 
>>>>> 
>>>> 
>>> 
>