[ruby-cvs:72927] shugo:r65827 (trunk): revert r65822

[shugo at ruby-lang.org]

shugo	2018-11-20 12:56:51 +0900 (Tue, 20 Nov 2018)

  New Revision: 65827

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=65827

  Log:
    revert r65822
    
    Because mon_initialized may be used to re-initialize copied objects intentionally.
    
    mon_initialize_spec.rb fails:
    
    1)
    MonitorMixin#mon_initialize can be called in initialize_copy to get a new Mutex and used with synchronize ERROR
    ThreadError: already initialized
    /home/shugo/src/ruby/lib/monitor.rb:255:in `mon_initialize'
    /home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:19:in `initialize_copy'
    /home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:28:in `initialize_dup'
    /home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:28:in `dup'
    /home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:28:in `block (2 levels) in <top (required)>'
    /home/shugo/src/ruby/spec/ruby/library/monitor/mon_initialize_spec.rb:4:in `<top (required)>'

  Removed files:
    trunk/test/monitor/test_monitor_mixin.rb
  Modified files:
    trunk/lib/monitor.rb