From: "J. Ryan Sobol" <ryansobol@...>
Date: 2005-12-24T07:45:30+09:00
Subject: Re: multithreaded file access

On Dec 23, 2005, at 5:23 PM, Ilmari Heikkinen wrote:

> On 12/23/05, J. Ryan Sobol <ryansobol@gmail.com> wrote:
>> On Dec 23, 2005, at 4:13 PM, Ilmari Heikkinen wrote:
>>> [kig@jugend:~] ruby fw_test.rb
>>> puts in different threads seems to be atomic
>>
>> Crafty test program.  Coincidentally, my results differ from yours.
>>
>> $ ruby fw_test.rb
>> puts in different threads isn't atomic
>> $ ruby -v
>> ruby 1.8.2 (2004-12-25) [powerpc-darwin8.3.0]
>
> Good! I thought it was odd that they seemed to be atomic..
>
> And now we know to mutex disk writes (or use flock.)
>
>> I'm getting 8 unique lines in File.readlines(fn).uniq, as opposed to
>> the 3 thread objects in ts.  Assuming I understand the program, that
>> means threads are not waiting their turn like they should.  FYI, I've
>> compiled my own ruby executable from DarwinPorts instead of using the
>> 'broken' one shipped in OS X Tiger.
>>
>> However, if I change the multiplication factor in line 3 to 655, then
>>
>> $ ruby fw_test.rb
>> puts in different threads seems to be atomic
>
> I don't know the reason (can guess, but too unsure)
> Explanation anyone?
>
>> ~ ryan ~
>>
>> PS - I love the 205+ MB of text this app generates! :-D
>
> Ilmari

Regardless, the important thing is to know that it seems file IO via  
puts is not thread safe, which I kind of assumed from the beginning.   
This begs the question: which methods, especially concerning file IO,  
are thread safe? (if any)

~ ryan ~