From: "none <" <tetsu.soh.dev@...>
Date: 2009-07-28T12:18:20+09:00
Subject: [ruby-core:24583] Re: [Bug #1525] Deadlock in Ruby 1.9's VM caused by ConditionVariable.wait and fork?

Hongli Lai wrote:
> none < wrote:
>   
>> Your test code was fine. The deadlock is not caused directly by your
>> code but may be related to the timer thread which is  created
>> automatically (by ruby processor) after forking a process. And creating
>> a native thread (Ruby1.8 was not native threaded, so it is ok.) is not
>> async-signal-safe. So deadlock occurs.
>>
>> What I mean is that user should try to avoid the following code:
>>    fork do
>>        Thread.new do   #Bad! Creating native threads is not safe.
>>           #some code
>>        end
>>    end
>>     
>
> In my test case, the forked child process does not create any new
> threads at all, but still deadlocks.
>   
I know. But Ruby processor fires a internel timer thread automatically.
And that's the reason of deadlock.

As I mentioned, right now, developer are trying to postpone the timer thread
generation. I think your problem can be fix by this way.

-Tetsu