The changes for 8000244 make the size of the global marking stack dependent upon the number of marking threads. It also added the capability to expand the marking stack in the event that concurrent marking overflowed the marking stack.

One of the code review comments was to reuse the previously committed/reserved space for the marking stack in the event that the expansion code fails to reserve or commit the new space rather than just abort. It is not a fatal error to reuse the previously committed space - marking will make progress albeit sub-optimally.