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

Jon Masamitsu jon.masamitsu at oracle.com
Fri Mar 4 23:44:58 UTC 2016


Change looks good.

One  issue for you consideration.


1042 void G1ConcurrentMark::register_concurrent_phase_end() {
1043 register_concurrent_phase_end_common(false);
1044 }
1046 void G1ConcurrentMark::register_concurrent_gc_end() {
1047 register_concurrent_phase_end_common(true);
1048 }

I understand that adding these functions is a style and
I've used  that style before but in this case it confuses
me.  Having register_concurrent_phase_end()
call register_concurrent_phase_end_common() makes sense
since their names are similar but I'm less clear
about register_concurrent_gc_end() calling

Maybe register_concurrent_gc_end() should be renamed

Or have two statics
static const bool StopTimer = true;
static const bool DontStopTime = false;

and then call



You could drop the "_common" part of the name.

As I said, it's a matter of style so you can choose.


On 03/02/2016 11:41 PM, 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

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