From: Joel VanderWerf <vjoel@...>
Date: 2006-11-16T10:13:10+09:00
Subject: Re: thread dump?

Eric Hodel wrote:
> On Oct 22, 2006, at 12:12 PM, Joel VanderWerf wrote:
>> cs5b@yahoo.com wrote:
>>> Hi there, I have a process that seems to be stuck somewhere. Is there
>>> the possibility of doing a thread dump to show where it is hanging on?
>>> Cheers -
>>> Christian
>>
>> Not in general, without a Thread#backtrace method. I've asked for it...
>>
>> http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/159482
>>
>> As noted in that post, you can destructively find out where the thread 
>> is by calling #raise on it. Just make sure the thread has an exception 
>> handler somewhere to print out the exception and backtrace.
> 
> $ ruby -e 't = Thread.start do sleep end; t.raise "hi"; t.value'
> -e:1: hi (RuntimeError)
>         from -e:1:in `value'
>         from -e:1

That doesn't tell you what line of code the thread is sleeping on, only 
what lines of code #raise and #value are called on. You lose the whole 
backtrace, in fact.

$ cat th.rb
t = Thread.start do
   sleep
end

t.raise "hi"
t.value

$ ruby th.rb
th.rb:5: hi (RuntimeError)
         from th.rb:6:in `value'
         from th.rb:6

-- 
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407