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ConcurrentModificationException from ThreadGroup.list #2446

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kares opened this issue Jan 9, 2015 · 0 comments · Fixed by #2451
Closed

ConcurrentModificationException from ThreadGroup.list #2446

kares opened this issue Jan 9, 2015 · 0 comments · Fixed by #2451
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@headius
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beginner core JRuby 1.7.x JRuby 9000
Milestone
JRuby 1.7.19

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@kares
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kares commented Jan 9, 2015

while the rubyThreadList field is a fully synchronized collection, iterator might still throw a CME

https://github.com/jruby/jruby/blob/jruby-1_7/core/src/main/java/org/jruby/RubyThreadGroup.java#L149

there's probably a typo the line above as it synchronizes on a local variable :

 RubyArray ary = RubyArray.newArray(getRuntime());
  synchronized (ary) {
WeakHashMap.java:882:in `nextEntry': java.util.ConcurrentModificationException
    from WeakHashMap.java:915:in `next'
    from RubyThreadGroup.java:149:in `list'
    from RubyThreadGroup$INVOKER$i$0$0$list.gen:-1:in `call'
    from JavaMethod.java:280:in `call'
    from CachingCallSite.java:306:in `cacheAndCall'
    from CachingCallSite.java:136:in `call'
    from CallNoArgNode.java:60:in `interpret'
    from CallNoArgBlockPassNode.java:53:in `interpret'
    from NewlineNode.java:105:in `interpret'
    from BlockNode.java:71:in `interpret'
    from ASTInterpreter.java:112:in `INTERPRET_BLOCK'
    from Interpreted19Block.java:206:in `evalBlockBody'
    from Interpreted19Block.java:157:in `yield'
    from Block.java:142:in `yield'
    from Mutex.java:149:in `synchronize'
    from Mutex$INVOKER$i$0$0$synchronize.gen:-1:in `call'

only seen this under high actor/fiber usage (Celluloid) ... reproduced on 1.7.16
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@headius headius

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beginner core JRuby 1.7.x JRuby 9000
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No need to synchronise a newly created local RubyArray Who828/jruby
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@headius @kares