# Thread deadlock problem **URL:** \ **Category:** Ruby\ **Created:** [September 11, 2007, 5:36am UTC](https://www.ruby-forum.com/t/thread-deadlock-problem/114305 "2007-09-11T05:36:24Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [September 11, 2007, 5:36am UTC](https://www.ruby-forum.com/t/thread-deadlock-problem/114305/1 "2007-09-11T05:36:24Z")
I made the following test: #------------------------------------------------------------------- require ‘thread’ mutex = Mutex.new c\_produce = ConditionVariable.new c\_consume = ConditionVariable.new full = false t1 = Thread.new do while true mutex.synchronize do c\_produce.wait mutex while full print ‘F’ full = true c\_consume.signal end #sleep 0.001 end end t2 = Thread.new do while true mutex.synchronize do c\_consume.wait mutex while !full print ‘.’ full = false c\_produce.signal end end end t1.join t2.join #------------------------------------------------------------------- This should be a classic producer/consumer problem solution. The output: F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.F.deadlock 0x2b68300: sleep:- - c:/ruby/projects/threads2.rb:9 deadlock 0x27bc74c: sleep:J(0x2b68300) (main) - c:/ruby/projects/ threads2.rb:27 deadlock 0x2b68274: sleep:- - c:/ruby/projects/threads2.rb:20 c:/ruby/projects/threads2.rb:20: Thread(0x2b68274): deadlock (fatal) What is wrong with the code? > ruby -v > ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32] Also, uncommenting a sleep from above makes the deadlocks disappear and everything works rather fine - is this just a matter of tweaking the probability? It ran for quite a long time (several minutes), that’s why I doubt this, but hey - I just might be completely wrong. Any ideas? ---
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [September 11, 2007, 6:45am UTC](https://www.ruby-forum.com/t/thread-deadlock-problem/114305/2 "2007-09-11T06:45:29Z")
On Sep 10, 2007, at 9:35 PM, removed\_email\_address@domain.invalid wrote: > ``` > print 'F' > print '.' > full = false > c_produce.signal > > ``` > > end > end > end > t1.join > t2.join it seems like you are making if very hard on yourself. why not something like this: cfp:~ \> cat a.rb require ‘thread’ q = SizedQueue.new 42 producer = Thread.new do loop do q.push Time.now.to\_f end end consumer = Thread.new do loop do p(( data = q.pop )) end end producer.join consumer.join ?? if you really want to roll your own stuff check out the code in thread.rb - the Queue and SizedQueue classes are basically the code you are writing above. cheers. a @ [http://drawohara.com/](http://drawohara.com/) ---
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [September 11, 2007, 9:24am UTC](https://www.ruby-forum.com/t/thread-deadlock-problem/114305/3 "2007-09-11T09:24:43Z")
What version of Ruby are you using ? The thread implementation has been broken in many ways since 1.8.6, so it can be the problem (I have a patched ruby 1.8.6 here with some fixes and it works fine) ---
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [September 11, 2007, 7:01pm UTC](https://www.ruby-forum.com/t/thread-deadlock-problem/114305/4 "2007-09-11T19:01:20Z")
On Tue, 11 Sep 2007 12:35:08 +0900, removed\_email\_address@domain.invalid wrote: > ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32] > > Also, uncommenting a sleep from above makes the deadlocks disappear > and everything works rather fine - is this just a matter of tweaking > the probability? It ran for quite a long time (several minutes), > that’s why I doubt this, but hey I think you at least need a newer patchlevel of 1.8.6; IIRC, there are bugs in the mutex implementation that shipped with 1.8.6p0. -mental ---
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [September 11, 2007, 3:36pm UTC](https://www.ruby-forum.com/t/thread-deadlock-problem/114305/5 "2007-09-11T15:36:42Z")
@ara > it seems like you are making if very hard on yourself. > No, this is just a test. I have another problem requiring the > synchronization. It is not working, so I made this test to see what is > I am doing wrong. It seems that it is not a problem with the other > code, but the part of the code that is similar to what I have made in > the above test. However, thanks for the pointers - I will take a look > at them and I might just find an answer. @Sylvain > What version of Ruby are you using ? > I have posted the output of > ruby -v which is: ruby 1.8.6 (2007-03-13 patchlevel 0) [i386-mswin32] Do you need some more info (and how can I obtain it)? Also, is there some good documentation about multi-threading in ruby, especially the synchronization part? I have looked at some tutorials (e.g. Programming Ruby: The Pragmatic Programmer’s Guide), but they are sparse on this topic (just a few examples, not even near to what I need). Any others? ---
**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\ **Post date:** [September 11, 2007, 9:20pm UTC](https://www.ruby-forum.com/t/thread-deadlock-problem/114305/6 "2007-09-11T21:20:40Z")
On Sep 11, 12:59 pm, MenTaLguY [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > -mental Thanks, that worked. I just downloaded patch 36 and it worked fine. _sigh_