From: Bertram Scharpf <lists@...>
Date: 2009-01-21T20:41:54+09:00
Subject: Re: Threads After Fork

Hi,

Am Mittwoch, 21. Jan 2009, 04:48:14 +0900 schrieb James Gray:
> On Jan 20, 2009, at 1:42 PM, Tim Pease wrote:
>> On Jan 20, 2009, at 8:55 AM, James Gray wrote:
>>
>>> printer = Thread.new do
>>>   10.times do
>>>     sleep 1
>>>     puts "Thread running in #{Process.pid}..."
>>>   end
>>> end
>>>
>>> fork do
>>>   p [Process.pid, printer.status]
>>>   printer.join
>>> end
>>>
>>> Are all other threads stopped as part of a process fork?
>>
>> fork doesn’t copy other threads.
>
> Man, I swear I've read that documentation 400 times now and just keep 
> missing that.

A soothing fact that even the well-experienced Ruby programmer
sometimes detects new aspects.

I think the amazing strike is that the variable containing the
Thread instance still exists whilst the Thread will surely be
dead. Joining a dead thread does just nothing. I reduced it to
these two lines:

  t = Thread.new do sleep 100 end
  fork do puts t.inspect end

Output:

  #<Thread:0x28456bcc dead>

Bertram


-- 
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de