RFR(S): 8149834: gc/shared/gcTimer.cpp:88 assert(_is_concurrent_phase_active) failed: A concurrent phase is not active

[Derek White]

Looks good to me!

  - Derek

On 3/3/16 2:41 AM, sangheon wrote:
> Hi all,
>
> Could I have a couple of reviews for this quick fix?
>
> There is a race between VMThread and ConcurrentMarkThread for 
> ConcurrentGCTimer.
> At the end of abort, VMThread is trying to end concurrent timer and if 
> ConcurrentMarkThread is trying to start or end concurrent phase, timer 
> related asserts will be fired.
> (Only ConcurrentMarkThread starts a concurrent phase)
> We have 3 different cases but the root cause is same[1].
>
> This proposal is introducing 3 phases of started, not started and 
> stopping for concurrent phase status.
> And the status is updated by cmpxchg.
>
> However, I think more proper fix would be eliminating the race.
> Currently G1CollectedHeap has ConcurrentGCTimer but it is mostly used 
> from ConcurrentMarkThread.
> So moving the timer and related routines to ConcurrentMark seems better.
> I filed a new RFE for this[2].
>
> Many thanks to Jon, Bengt(base patch as well) and StefanK for the 
> discussion.
>
> CR: https://bugs.openjdk.java.net/browse/JDK-8151085
> Webrev: http://cr.openjdk.java.net/~sangheki/8149834/webrev.00
> Testing: JPRT, local test with adding some sleep at vm code.
>
> [1] Related bugs:
> https://bugs.openjdk.java.net/browse/JDK-8145996
> https://bugs.openjdk.java.net/browse/JDK-8150819
>
> [2] RFE for proper fix:
> https://bugs.openjdk.java.net/browse/JDK-8151085
>
> Thanks,
> Sangheon
>
>
>
>