[jdk25u] RFR: 8370049: [s390x] G1 barrier compareAndExchange does not return old value when compareExchange fails

[Vladimir Petko]

Backporting JDK-8370049 to avoid hard-to-diagnose synchronisation issues on S390x. 

S390x tests:


==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
   jtreg:test/hotspot/jtreg/compiler/gcbarriers/TestG1BarrierGeneration.java
                                                         1     1     0     0     0   
==============================
TEST SUCCESS


Tier1:


==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
   jtreg:test/hotspot/jtreg:tier1                     3027  2383     0     0   644   
>> jtreg:test/jdk:tier1                               2527  2421     2     0   104 <<
   jtreg:test/langtools:tier1                         4654  4645     0     0     9   
   jtreg:test/jaxp:tier1                                 0     0     0     0     0   
   jtreg:test/lib-test:tier1                            37    37     0     0     0   
==============================
TEST FAILURE

Unrelated failure:

==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
   jtreg:test/jdk/java/lang/ProcessBuilder/Basic.java
>>                                                       2     0     2     0     0 <<
==============================
TEST FAILURE

It will be addressed by https://github.com/openjdk/jdk25u/pull/334


Tier2 tests:


==============================
Test summary
==============================
   TEST                                              TOTAL  PASS  FAIL ERROR  SKIP   
>> jtreg:test/hotspot/jtreg:tier2                      946   755     1     0   190 <<
>> jtreg:test/jdk:tier2                               4319  4076     3     0   240 <<
   jtreg:test/langtools:tier2                           14    12     0     0     2   
   jtreg:test/jaxp:tier2                               517   516     0     0     1   
   jtreg:test/docs:tier2                                 4     0     0     0     4   
==============================
TEST FAILURE



Unrelated failures:
1. applications/ctw/modules/jdk_jfr.java                                                      Failed. Execution failed: `main' threw exception: java.lang.AssertionError: There were 1 errors:[{modules_jdk_jfr_0: failed during compilation of class ... jdk/jfr/internal/jfc/JFC}] - existing issue https://bugs.openjdk.org/browse/JDK-8352567 
2. java/net/Inet6Address/B6206527.java                                                                      Failed. Execution failed: `main' threw exception: java.net.SocketException: Duplicate link local addresses: must specify scope-id
3. java/net/Inet6Address/Scoping.java                                                                       Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: Failed: /[fe80:0:0:0:ca:9ff:fe00:6d0c]:0count: 0
4. java/net/NetworkInterface/UniqueMacAddressesTest.java                                                    Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: mac address uniqueness test failed

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

Commit messages:
 - Backport 5609ee11a2daf888d02c0c1b2b70eb4df817582c

Changes: https://git.openjdk.org/jdk25u/pull/330/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u&pr=330&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370049
  Stats: 21 lines in 2 files changed: 20 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk25u/pull/330.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u.git pull/330/head:pull/330

PR: https://git.openjdk.org/jdk25u/pull/330