Heads-up: guarantee(obj->mark() == markOopDesc::encode(mid)) failed

[Aleksey Shipilev]

On 06/12/2017 11:18 AM, Aleksey Shipilev wrote:
> Hey Roman,
> 
> I think ShenandoahMergeSafepointCleanup has a bug somewhere, because this seems
> to fail with moderate frequency:
> 
> $ build/linux-x86_64-normal-server-fastdebug/images/jdk/bin/java -jar
> ~/Install/jcstress/jcstress-tests-all-2017-06-12.jar --jvmArgs
> "-XX:+UseShenandoahGC -XX:ShenandoahGCHeustics=aggressive
> -XX:+UnlockExperimentalVMOptions -XX:+ShenandoahMergeSafepointCleanup" -t
> WeakReference -m stress
> 
> 
> #  Internal Error
> (/home/shade/trunks/shenandoah-jdk9/hotspot/src/share/vm/runtime/synchronizer.cpp:1611),
> pid=12272, tid=12292
> #  guarantee(obj->mark() == markOopDesc::encode(mid)) failed: invariant
> 
> 
> http://cr.openjdk.java.net/~shade/shenandoah/hs_err_pid12272.log
> 
> Please take a look?

It seems to always crash like this:
 https://paste.fedoraproject.org/paste/x2hklWE3oq9DOyn1FNfCOQ

I.e. we try to deflate some monitor that seems already deflated, and the failure
always happens at full GC that follows cancellation. A clue, perhaps?

-Aleksey