When we encounter marking stack overflow during precleaning of Reference lists, we were using the overflow list mechanism, which can cause problems on account of mutating the mark word of the header because of conflicts with mutator accesses and updates of that field. Instead we should use the usual mechanism for overflow handling in concurrent phases, namely dirtying of the card on which the overflowed object lies. Since precleaning effectively does a form of discovered list processing, albeit with discovery enabled, we needed to adjust some code to be correct in the face of interleaved processing and discovery.
Reviewed-by: apetrusenko, jcoomes
Construct the relevant CMSIsAliveClosure used by CMS during parallel reference processing with the correct span. It had incorrectly been constructed with an empty span, a regression introduced in 6417901.
Reviewed-by: jcoomes
The option CMSInitiatingPermOccupancyFraction now controls perm triggering threshold. Even though the actual value of the threshold has not yet been changed, so there is no change in policy, we now have the infrastructure in place for dynamically deciding when to collect the perm gen, an issue that will be addressed in the near future.
Reviewed-by: jmasa
