* ext/thread/thread.c (rb_szqueue_push): check GET_SZQUEUE_WAITERS
  instead of GET_QUEUE_WAITERS to prevent deadlock. Patch by Eric Wong.
  [Bug #9302] [ruby-core:59324]

* test/thread/test_queue.rb: add test

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@44583 b2dd03c8-39d4-4d8f-98ff-823fe69b080e