From: ara.t.howard@...
Date: 2006-08-22T09:09:21+09:00
Subject: Re: [BUG] thwait

On Tue, 22 Aug 2006, Justin Collins wrote:

> Ara.T.Howard wrote:
>> 
>> i'm unsure if this should be expected to cause deadlock or not?
>> 
>>   ruby -r thwait -e'  ThWait.all_waits(*Array.new(42){ 
>> Thread.new{Thread.stop} })  '
>> 
>> for 1.8.1 - 1.8.4 it does.
>> 
>> thoughts?
>> 
>> -a
>
> Seems like it would. You create a bunch of threads, tell them not to run, 
> then tell the main thread to wait on all the stopped threads.
>
> There's no way for this program to complete or continue.

it seems like it should just hang then.  otherwise this program wouldn't be
able to work

   harp:~ > cat a.rb
   require 'thwait'

   loop{
     stopped = Thread.new{ Thread.stop }

     notify = Thread.new{ stopped.wakeup }

     ThWait.all_waits stopped
   }

this code __should__ be able to run - but it won't.  the docs say:

   harp:~ > ri ThreadsWait
   ----------------------------------------------------- Class: ThreadsWait
        This class watches for termination of multiple threads. Basic
        functionality (wait until specified threads have terminated) can be
        accessed through the class method ThreadsWait::all_waits. Finer
        control can be gained using instance methods.

a sleeping thread has not terminated, but whose to say it won't at some point
in the future?

for instance.  this is valid ruby

   ruby -e'  Thread.new{ sleep }.join  '

it just hangs forever.  similarly i feel that

   ThWait.all_waits Thread.new{ sleep }

should also hang - not deadlock.

regards.


-a
-- 
to foster inner awareness, introspection, and reasoning is more efficient than
meditation and prayer.
- h.h. the 14th dali lama