RFR: 8289220: [Shenandoah] TestAllocObjectArrays fails intermittently [v2]

[SUN Guoyun]

> 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             }

SUN Guoyun has updated the pull request incrementally with one additional commit since the last revision:

  8289220: [Shenandoah] TestAllocObjectArrays fails intermittently

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14211/files
  - new: https://git.openjdk.org/jdk/pull/14211/files/31137f12..51883706

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14211&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14211&range=00-01

  Stats: 20 lines in 3 files changed: 14 ins; 4 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/14211.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14211/head:pull/14211

PR: https://git.openjdk.org/jdk/pull/14211