<i18n dev> testcase failure java/util/Locale/Bug6989440.java

[Chris Hegarty]

David,

Expanding (more threads and more runs) and running this test on one of 
our dual core Linux x64 boxes, reproduce the CME about one in every ten 
runs.

I instrumented where the CME was being created to determine the 
expected/actual modcount:
         final void checkForComodification() {
              if (modCount != expectedModCount)
-                throw new ConcurrentModificationException();
+                throw new ConcurrentModificationException("Expected: " 
+ expectedModCount +
+                                                          ", got: " + 
modCount);

I see several exceptions, similar to the following (numbers vary):

Exception in thread "Thread-23" 
java.util.ConcurrentModificationException: Expected: 96, got: 156
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:819)
	at java.util.ArrayList$Itr.next(ArrayList.java:791)
	at java.util.AbstractCollection.addAll(AbstractCollection.java:333)
	at java.util.HashSet.<init>(HashSet.java:117)
	at 
sun.util.LocaleServiceProviderPool.getAvailableLocales(LocaleServiceProviderPool.java:206)
	at Interrupter$TestThread.run(Interrupter.java:49)


There would appear to be 156 JRE Locales ( at least on this system ), 
modCount is incremented for each add(), but when the iterator is created 
( implicitly during the HastSet.addAll ) it sees a different value for 
modCount.

I think there is a visibility issue here. availableJRELocales is 
volatile, but the List reference returned from getJRELocales is not. In 
the case where availableJRELocales is not null there will be no memory 
barrier to force a HB relationship. Or maybe I've gotten this wrong? His 
is quite bizarre, or maybe it is just the overly complicated use of 
locking/DCL in this class.

-Chris.

On 10/ 5/11 07:01 PM, David Holmes wrote:
> This might not be related to the CME problem, but here:
>
> public static LocaleServiceProviderPool getPool(Class<? extends
> LocaleServiceProvider> providerClass) {
> LocaleServiceProviderPool pool = poolOfPools.get(providerClass);
> if (pool == null) {
> LocaleServiceProviderPool newPool =
> new LocaleServiceProviderPool(providerClass);
> pool = poolOfPools.put(providerClass, newPool);
> if (pool == null) {
> pool = newPool;
> }
> }
>
> return pool;
> }
>
> we should probably be using poolOfPools.putIfAbsent(providerClass, newPool)
>
> David
>
> On 6/10/2011 3:35 AM, Naoto Sato wrote:
>> I will look into this. Reopened the original CR.
>>
>> Naoto
>>
>> On 10/5/11 9:58 AM, Alan Bateman wrote:
>>> Chris Hegarty wrote:
>>>> Alan, Naoto, David
>>>>
>>>> I filed CR 7098100: java/util/Locale/Bug6989440.java fails
>>>> intermittently.
>>>>
>>>> If you're ok with it please review the patch (below) and I can push it
>>>> to the tl repo. Job done!
>>> I assume there is also some underlying issue in the Locale code and this
>>> might get hidden if we fix the test (I"ve no objection to fixing the
>>> test of course, just thinking that we should study the Locale code to
>>> try to identify the deadlock or hang or whatever it is that is causing
>>> the threads in this test not to terminate).
>>>
>>> -Alan
>>