RFR: 8215773: applications/kitchensink/Kitchensink.java crash with "assert(ZAddress::is_marked(addr)) failed: Should be marked"

[coleen.phillimore at oracle.com]

Hi Erik,  This is kind of creepy.  They use the dead mirror and call 
identity hash on it, which writes to the dead mirror.

Are these functions called at a safepoint?  Maybe JFR could do something 
different here.

Coleen


On 1/4/19 5:10 AM, Erik Österlund wrote:
> Hi,
>
> During SystemDictionary::do_unloading(), JFR pokes around at the dead 
> mirror oops that died due to class unloading.
> The mirror is loaded without AS_NO_KEEPALIVE, which makes ZGC load 
> barriers a bit sad, because they dislike loading dead oops.
>
> The solution is to load these mirrors with AS_NO_KEEPALIVE decorators, 
> indicating that it is okay for them to be dead as we are only peeking 
> at them. This is fine to do during concurrent execution by the GC 
> thread that is performing class unloading, and hence controls the GC 
> cycle, making sure that the memory of the dead oops is not reclaimed 
> until the accesses have safely finished.
>
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8215773
>
> Webrev:
> http://cr.openjdk.java.net/~eosterlund/8215773/webrev.00/
>
> Manually ran kitchensink 24 hours to make sure this doesn't happen 
> again. And hs-tier1-6 on linux.
>
> Thanks,
> /Erik