RFR: 8288282: Zero-release build is broken after JDK-8279047 due to UseHeavyMonitors is read-only [v2]

[Aleksey Shipilev]

On Sun, 12 Jun 2022 04:42:49 GMT, Jie Fu <jiefu at openjdk.org> wrote:

>> Hi all,
>> 
>> Zero-release build is broken after JDK-8279047.
>> After JDK-8279047, `UseHeavyMonitors` becomes read-only in PRODUCT VMs.
>> 
>> But for Zero, `UseHeavyMonitors` needs to be reset if `DiagnoseSyncOnValueBasedClasses != 0`.
>> 
>>   // If lock diagnostics is needed, always call to runtime
>>   if (DiagnoseSyncOnValueBasedClasses != 0) {
>>     FLAG_SET_DEFAULT(UseHeavyMonitors, true);
>>   }
>> 
>> 
>> I never hear that people would DiagnoseSyncOnValueBasedClasses with zero vms.
>> So in order to expire `UseHeavyMonitors` for all PRODUCT VMs, I suggest disabling lock diagnostics for zero vms.
>> 
>> Thanks.
>> Best regards,
>> Jie
>
> Jie Fu has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Only disable lock diagnostics for zero product vms

Unfortunately, that would break:


CONF=linux-x86_64-zero-release make exploded-test TEST=runtime/Monitor/SyncOnValueBasedClassTest.java

java.lang.RuntimeException: 'fatal error: Synchronizing on object' missing from stdout/stderr 


I think the patch should just be:


diff --git a/src/hotspot/cpu/zero/vm_version_zero.cpp b/src/hotspot/cpu/zero/vm_version_zero.cpp
index 5c2a0a3d5d2..df6c7f0eba2 100644
--- a/src/hotspot/cpu/zero/vm_version_zero.cpp
+++ b/src/hotspot/cpu/zero/vm_version_zero.cpp
@@ -47,7 +47,8 @@ void VM_Version::initialize() {
 
   // If lock diagnostics is needed, always call to runtime
   if (DiagnoseSyncOnValueBasedClasses != 0) {
-    FLAG_SET_DEFAULT(UseHeavyMonitors, true);
+    warning("Lock diagnostics is not available on this CPU");
+    FLAG_SET_DEFAULT(DiagnoseSyncOnValueBasedClasses, 0);
   }
 
   if (UseAESIntrinsics) {
diff --git a/test/hotspot/jtreg/runtime/Monitor/SyncOnValueBasedClassTest.java b/test/hotspot/jtreg/runtime/Monitor/SyncOnValueBasedClassTest.java
index 394a92c0398..1793ba2e0d7 100644
--- a/test/hotspot/jtreg/runtime/Monitor/SyncOnValueBasedClassTest.java
+++ b/test/hotspot/jtreg/runtime/Monitor/SyncOnValueBasedClassTest.java
@@ -31,6 +31,7 @@ import java.util.stream.*;
  * @bug 8242263
  * @summary Exercise DiagnoseSyncOnValueBasedClasses diagnostic flag
  * @requires vm.flagless
+ * @requires vm.flavor != "zero"
  * @library /test/lib
  * @run driver/timeout=180000 SyncOnValueBasedClassTest
  */

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

Changes requested by shade (Reviewer).

PR: https://git.openjdk.org/jdk/pull/9138