From: Aristarkh A Zagorodnikov <xm@...3d.ru>
Date: 2001-04-29T06:50:39+09:00
Subject: [ruby-talk:14389] Ruby BUG (marshaling)


        Hello, everyone!

I'm too angry right now, so I'll be short :)

I need to allow simultaneous file updates (update order does not mean).
I do the following:
#   Extend File class
class File
#   Methods
#       Open file, locking it
    def File.open_locked(name, mode)
        file = File.open name, mode
        file.flock LOCK_EX
        file.seek 0, (/^a/ =~ mode ? SEEK_END : SEEK_SET)
        if block_given?
         begin
             yield file
   ensure
             file.close
   end
        else
            file
        end
    end
end

Then I use open_locked in this way:
File.open_locked @@path, 'rb' do |file| @@options = Marshal.load file end
.....
File.open_locked @@path, 'wb' do |file| Marshal.dump @@options, file end

Seems right, isn't it ?

But, when running the script simultaneousle 50 times, data gots thrashed
resulting sometimes even in corrupted file!
It seems that Marshal.dump unlocks the file or whatever?
I think that this should be investigated immediately, and a solution should
be proposed to matz (I'll try to take a look at C source, but don't cont on
me too much)

Thanks for your attention
Aristarkh A Zagorodnikov