more explicit synchronization.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58356 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
more explicit synchronization.
On some systems (for example, high load average systems) can't start Thread
correctly and can't wait r.gets in invoked Thread.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58356 b2dd03c8-39d4-4d8f-98ff-823fe69b080e