use Queue for inter-thread synchronization.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63085 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
use Queue for inter-thread synchronization.
"while" synchronization, but should use Queue.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63085 b2dd03c8-39d4-4d8f-98ff-823fe69b080e