# Problems with Mutex and ConditionVariable under IronRuby

**URL:** <https://www.ruby-forum.com/t/problems-with-mutex-and-conditionvariable-under-ironruby/156755>\
**Category:** IronRuby\
**Created:** [January 2, 2009, 1:45pm UTC](https://www.ruby-forum.com/t/problems-with-mutex-and-conditionvariable-under-ironruby/156755 "2009-01-02T13:45:05Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\
**Post date:** [January 2, 2009, 1:45pm UTC](https://www.ruby-forum.com/t/problems-with-mutex-and-conditionvariable-under-ironruby/156755/1 "2009-01-02T13:45:05Z")

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Hello,

I was playing with threads under IronRuby but it seems like I have  
stumbled on problems with Mutex and ConditionVariable. At first I  
thought the problem was related to my code even if it actually worked  
flawlessy for months under MRI 1.8.6 and it runs fine under the latest  
JRuby, so I tried to run the most basic example of using these two  
classes (a classic one:  
[http://www.rubycentral.com/pickaxe/tut\_threads.html#UF](http://www.rubycentral.com/pickaxe/tut_threads.html#UF)) but the  
problems still persist.

At first I thought it was some kind of deadlock given that the output  
obtained by running the code with ir.exe is as follows:

C:\Sviluppo\ironruby\SVN\trunk\build\debug\>ir T002.rb  
A: I have critical section, but will wait for cv  
(Later, back at the ranch…)  
B: Now I am critical, but am done with cv

(note that the process remains stuck there)

So I went debugging with Visual Studio and this is what I got in the  
output window:  
[http://gist.github.com/raw/42514/8d38b629e8ae62d9c4bece398a4041b036d28f12](http://gist.github.com/raw/42514/8d38b629e8ae62d9c4bece398a4041b036d28f12)

To make it short, the reported exception is thrown when the ruby code  
calls ConditionVariable#signal and IronRuby internally calls  
Monitor.Pulse on the Mutex instance:

[RubyMethod(“signal”)]  
public static RubyConditionVariable/_!_/  
Signal(RubyConditionVariable/_!_/ self) {  
RubyMutex m = self.\_mutex;  
if (m != null) {  
Monitor.Pulse(m);  
}  
return self;  
}

It seems like the Monitor is not aware of being in a synchronized  
block of code (or is not in a critical section at all). Any clues?

Thanks,

Daniele

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<div class="post-metadata">

**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\
**Post date:** [January 2, 2009, 5:57pm UTC](https://www.ruby-forum.com/t/problems-with-mutex-and-conditionvariable-under-ironruby/156755/2 "2009-01-02T17:57:23Z")

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It looks like ConditionVariable.wait isn’t implemented in a way that’s  
consistent with the spec. Please file a bug report on RubyForge.

I’m a bit surprised by the semantics of this class. It doesn’t appear  
possible to use it safely unless there’s at least one additional level  
of locking.

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<div class="post-metadata">

**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\
**Post date:** [January 2, 2009, 9:07pm UTC](https://www.ruby-forum.com/t/problems-with-mutex-and-conditionvariable-under-ironruby/156755/3 "2009-01-02T21:07:27Z")

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Thanks for a very detailed bug report!

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<div class="post-metadata">

**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\
**Post date:** [January 2, 2009, 8:41pm UTC](https://www.ruby-forum.com/t/problems-with-mutex-and-conditionvariable-under-ironruby/156755/4 "2009-01-02T20:41:34Z")

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On Fri, Jan 2, 2009 at 17:56, Curt H. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> It looks like ConditionVariable.wait isn’t implemented in a way that’s consistent with the spec. Please file a bug report on RubyForge.

Bug report filed.

While I was at it, I filed another bug report about potential  
multithreading issues when modules are initialized by IronRuby. See:  
[http://rubyforge.org/tracker/index.php?func=detail&aid=23408&group\_id=4359&atid=16798](http://rubyforge.org/tracker/index.php?func=detail&aid=23408&group_id=4359&atid=16798)

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<div class="post-metadata">

**Author:** ![murena](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/7ba0ec/32.png) [@murena](https://www.ruby-forum.com/u/murena)\
**Post date:** [January 3, 2009, 12:17pm UTC](https://www.ruby-forum.com/t/problems-with-mutex-and-conditionvariable-under-ironruby/156755/5 "2009-01-03T12:17:24Z")

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On Fri, Jan 2, 2009 at 21:03, Curt H. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
wrote:

> Thanks for a very detailed bug report!

I just filed another bug 🙂

“A Fixnum fails to grow to a Bignum when using the left shift operator”  
[http://rubyforge.org/tracker/index.php?func=detail&aid=23414&group\_id=4359&atid=16798](http://rubyforge.org/tracker/index.php?func=detail&aid=23414&group_id=4359&atid=16798)

I tackled this bug when I noticed strange behaviours/errors under  
IronRuby while using ruby’s IPAddr class.