I agree with Antoine's comment on the PR: this seems like this should only go into 3.7.  From the description here, it sounds like this is an edge-case problem that hasn't come up before as an issue.  Let's do the right thing in master (for 3.7) and try to come up with a workaround for 3.6.x (like increasing the stack size).  And doing that does not prevent us from deciding later to backport to 3.6.x once we have some experience with the changes in master.