class ActiveSupport::Concurrency::ShareLock

def yield_shares(purpose: nil, compatible: [], block_share: false)
  loose_shares = previous_wait = nil
  synchronize do
    if loose_shares = @sharing.delete(Thread.current)
      if previous_wait = @waiting[Thread.current]
        purpose = nil unless purpose == previous_wait[0]
        compatible &= previous_wait[1]
      end
      compatible |= [false] unless block_share
      @waiting[Thread.current] = [purpose, compatible]
    end
    @cv.broadcast
  end
  begin
    yield
  ensure
    synchronize do
      wait_for(:yield_shares) { @exclusive_thread && @exclusive_thread != Thread.current }
      if previous_wait
        @waiting[Thread.current] = previous_wait
      else
        @waiting.delete Thread.current
      end
      @sharing[Thread.current] = loose_shares if loose_shares
    end
  end
end