String#<< and Ruby threads

mrkohrea · September 5, 2008, 10:08pm

This gist code raises java.lang.ArrayOutOfBounds exception:

gist.github.com

https://gist.github.com/michaelklishin/30c7b6e4f0473a8bab5c

gistfile1.rbx

buffer = ""
threads = []
100.times do 
  threads << Thread.new do 
    1000.times { buffer << "This is a test" }
  end
end

threads.each{ |t| t.join }

If you change << to += though, the code does not raise.

Here’s the stack trace:

gist.github.com

https://gist.github.com/9012

gistfile1.txt

Exception in thread "Ruby Thread13839941" java.lang.ArrayIndexOutOfBoundsException
	at java.lang.System.arraycopy(Native Method)
	at org.jruby.RubyString.cat(RubyString.java:622)
	at org.jruby.RubyString.append(RubyString.java:1105)
	at org.jruby.RubyString.concat(RubyString.java:1117)
	at org.jruby.RubyStringInvoker$concat_method_1_0.call(Unknown Source)
	at org.jruby.runtime.CallSite$InlineCachingCallSite.call(CallSite.java:381)
	at ruby.Users.antares.dev.experiments.thread_safe_array.block_2$RUBY$__block__(thread_safe_array.rb:5)
	at ruby.Users.antares.dev.experiments.thread_safe_arrayBlockCallback$block_2$RUBY$__block__xx1.call(Unknown Source)
	at org.jruby.runtime.CompiledBlock.yield(CompiledBlock.java:100)

This file has been truncated. show original

Does it look like a JRuby problem or am I ignorant about something
with Ruby threads?

This issue breaks Merb applications running on JRuby:
http://snipr.com/3nfcg

MK

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mrkohrea · September 6, 2008, 2:24am

Michael K. wrote:

This issue breaks Merb applications running on JRuby:
http://snipr.com/3nfcg

File it as a bug. We don’t make guarantees about one thread stepping on
another thread as far as the contents of data structures go, but we
should never throw these kinds of errors and leave you with completely
unusable data structures. At worse, you should get a (Ruby) exception
about concurrency.

Also it may be worth filing it as a bug with Merb folks. I know they’re
keep to avoid situations that are likely to cause concurrency problems.
So there’s probably fixes to be done on both sides.

Charlie

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mrkohrea · September 6, 2008, 8:25am

Michael K. wrote:

This issue breaks Merb applications running on JRuby:
http://snipr.com/3nfcg

Wow, I obviously didn’t look at your last link. So it’s already reported
to the merb guys. Ok, so just file one for us and we’ll get it resolved.

Charlie

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mrkohrea · September 6, 2008, 8:44am

Charles Oliver N. wrote:

with Ruby threads?

This issue breaks Merb applications running on JRuby:
http://snipr.com/3nfcg

Wow, I obviously didn’t look at your last link. So it’s already reported
to the merb guys. Ok, so just file one for us and we’ll get it resolved.

FWIW, I also talked to Yehuda about it and he said he’d bump it up on
the priority list. So we just need to give String some TLC and both ends
ought to be good to go.

Thanks for pointing it out.

Charlie

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String#<< and Ruby threads

This issue breaks Merb applications running on JRuby: http://snipr.com/3nfcg

This issue breaks Merb applications running on JRuby:
http://snipr.com/3nfcg