MacBook Pro Early 2011, Lion, REE 2011.03, Mongo, forking #=> Errno::EINVAL

einval.rb

#!/usr/bin/env ruby

require 'rubygems'
require 'bundler/setup'
require 'mongo'

@conn = Mongo::Connection.new
@db = @conn['supply_chain_development']

puts @db['properties'].find.to_a.size

pid = fork do
  puts @db['properties'].find.to_a.size
  exit
end

Process.waitpid pid

puts "end"

# forked process crashes with:
# gems/mongo-1.3.1/lib/../lib/mongo/util/pool.rb:131:in `close': Invalid argument (Errno::EINVAL)
#   from gems/mongo-1.3.1/lib/../lib/mongo/util/pool.rb:131:in `checkout_existing_socket'
#   from gems/mongo-1.3.1/lib/../lib/mongo/util/pool.rb:154:in `checkout'
#   from gems/mongo-1.3.1/lib/../lib/mongo/util/pool.rb:152:in `synchronize'
#   from gems/mongo-1.3.1/lib/../lib/mongo/util/pool.rb:152:in `checkout'
#   from gems/mongo-1.3.1/lib/../lib/mongo/util/pool.rb:145:in `loop'
#   from gems/mongo-1.3.1/lib/../lib/mongo/util/pool.rb:145:in `checkout'
#   from gems/mongo-1.3.1/lib/../lib/mongo/connection.rb:579:in `checkout_reader'
#   from gems/mongo-1.3.1/lib/../lib/mongo/connection.rb:477:in `receive_message'
#   from gems/mongo-1.3.1/lib/../lib/mongo/cursor.rb:407:in `send_initial_query'
#   from gems/mongo-1.3.1/lib/../lib/mongo/connection.rb:609:in `instrument'
#   from gems/mongo-1.3.1/lib/../lib/mongo/cursor.rb:406:in `send_initial_query'
#   from gems/mongo-1.3.1/lib/../lib/mongo/cursor.rb:371:in `refresh'
#   from gems/mongo-1.3.1/lib/../lib/mongo/cursor.rb:87:in `next_document'
#   from gems/mongo-1.3.1/lib/../lib/mongo/cursor.rb:248:in `each'
#   from gems/mongo-1.3.1/lib/../lib/mongo/cursor.rb:267:in `to_a'
#   from gems/mongo-1.3.1/lib/../lib/mongo/cursor.rb:267:in `to_a'
#   from ./einval.rb:13
#   from ./einval.rb:12:in `fork'
#   from ./einval.rb:12