<i18n dev> RFR: 8289220: [Shenandoah] TestAllocObjectArrays fails intermittently

[SUN Guoyun]

On Tue, 30 May 2023 08:49:35 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> command: make test CONF=fastdebug JTREG="VM_OPTIONS=-Xcomp" TEST=gc/TestAllocHumongousFragment.java
>> error info: 
>> 
>> Caused by: java.lang.NullPointerException: Cannot invoke "sun.util.locale.BaseLocale.getVariant()" because "base" is null
>> at java.base/java.util.Locale.forLanguageTag(Locale.java:1802)
>> at java.base/sun.util.cldr.CLDRBaseLocaleDataMetaInfo.<clinit>(CLDRBaseLocaleDataMetaInfo.java:41)
>> ... 24 more
>> 
>> Note that the test runs with -XX:ShenandoahGCHeuristics=aggressive -XX:+ShenandoahOOMDuringEvacALot and SoftReferences are involved (LocaleObjectCache uses SoftReferences, used by printf method called in getRandomInstance(Utils.java:511)).
>> 
>> Maybe we have to deal with the case where the getBaseLocale() return value is null. the call stack is:
>> 
>> 	at java.base/sun.util.locale.LocaleObjectCache.get(LocaleObjectCache.java:64)
>> 	at java.base/sun.util.locale.BaseLocale.getInstance(BaseLocale.java:169)
>> 	at java.base/sun.util.locale.InternalLocaleBuilder.getBaseLocale(InternalLocaleBuilder.java:524)
>> 	at java.base/java.util.Locale.forLanguageTag(Locale.java:1874)
>> 
>> in LocaleObjectCache.java:64
>> 
>> 	 62             if (key == null || newVal == null) {                                
>> 	 63                 // subclass must return non-null key/value object               
>> 	 64                 return null; // run here
>> 	 65             }
>
> I don't think Locale.forLanguageTag is specified to return null so you might have to do a bit more analysis to see what this issue is about. There are soft refs usages in the locale and it could be that there is some that doesn't handle cases where the ref is cleared.

as @AlanBateman said, this patch may not be the radical solution.  But once executed here, the ` return null` should be handled.

 62             if (key == null || newVal == null) {                                
 63                 // subclass must return non-null key/value object               
 64                 return null; // then what we can do?
 65             }

-XX:ShenandoahGCHeuristics=aggressive -XX:+ShenandoahOOMDuringEvacALot can trigger frequent GC without caring if the memory is really low. So the problem of soft references can be exposed. I suspect that this code is not executed under normal circumstances, so there is no exposure problem.

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PR Comment: https://git.openjdk.org/jdk/pull/14211#issuecomment-1568109270