On the VM barrier waiting, it needs to store machine context
as a GC root.

Also it needs to wait for barrier synchronization correctly
by `while` (for continuous barrier sync by another ractor).

This is why GC marking misses are occerred on ARM machines.
like: https://rubyci.s3.amazonaws.com/fedora40-arm/ruby-master/log/20240702T063002Z.fail.html.gz