RFR (S): 8191129 - AARCH64: Invalid value passed to critical JNI function

[Vladimir Ivanov]

>> bug: https://bugs.openjdk.java.net/browse/JDK-8191129
>> webrev: http://cr.openjdk.java.net/~dchuyko/8191129/webrev.00/
>> 1. Platform specific part
>>
>> Original fix from JDK-8167409 was imported, it makes failures more 
>> deterministic: Unimplemented() or ShouldNotReachHere(). Implementation 
>> of the feature is not complete so another change is to forcibly set 
>> CriticalJNINatives to false during initialization.
>>
> 
> Do you want to print a warning if the flag was set to true on the 
> command-line?

IMO it should be:
   if (CriticalJNINatives) {
     warning("CriticalJNINatives aren't supported");
     FLAG_SET_DEFAULT(CriticalJNINatives, false);
   }

There's on point in enabling it if it is known the functionality is broken.

Also, I question putting it into VM_Version::initialize().

I haven't found a proper place for such checks, but 
VM_Version::get_processor_features() is where most of the 
platform-specific setup is performed (besides *_pd).

Better to hear from aarch64 port maintainers where they prefer to see it.

>> 2. Common part (tests)
>>
>> Tests in criticalnatives read CriticalJNINatives flag using WhiteBox 
>> and ignore values check if the flag is false.
>>
> 
> Would "@requires vm.opt.CriticalJNINatives" also work?

I'd prefer to see the test explicitly specifying -XX:+CriticalJNINative 
and excluded on aarch64 (@requires os.arch != aarch64) until the missing 
functionality is implemented there.

But I'm fine with "@requires vm.opt.CriticalJNINatives" as well.

Best regards,
Vladimir Ivanov