merge revision(s) 57595: [Backport #8996]
check thread deadness correctly.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@58108 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 57595: [Backport #8996]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@58108 b2dd03c8-39d4-4d8f-98ff-823fe69b080e