RFR: JDK-8276422 Add command-line option to disable finalization [v3]

[David Holmes]

Hi Mandy,

On 19/11/2021 6:16 am, Mandy Chung wrote:
> On Thu, 18 Nov 2021 06:49:03 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:
> 
>>> src/hotspot/share/prims/jvm.cpp line 694:
>>>
>>>> 692:
>>>> 693: JVM_ENTRY(jboolean, JVM_IsFinalizationEnabled(JNIEnv * env))
>>>> 694: return InstanceKlass::finalization_enabled() ? JNI_TRUE : JNI_FALSE;
>>>
>>> missing indentation
>>
>> I think this could just be `return InstanceKlass::finalization_enabled();`.  There is lots of code in this file and elsewhere that assumes C++ `bool` converts to `jboolean` appropriately.
> 
> One typical way for VM to pass the arguments to the library is via private system properties.   System::initPhase1 will save the VM properties in `jdk.internal.misc.VM` and filters out the private properties from the system properties returned from System::getProperties (see System::createProperties).

The Finalizer class is initialized before initPhase1() happens. So to 
use a property the Holder class had to be introduced to be initialized 
after initPhase1().

There is always a choice of having the VM push up a system property to 
the Java code, or the Java code calling down to query the VM. The VM 
call seems simpler/cheaper/cleaner in this case.

Cheers,
David

> You can query the flag via `jdk.internal.misc.VM.getProperty("jdk.finalization.disabled")` for example.
> 
> I don't see any issue moving the Finalizer class initialization after initPhase1 since there is no finalizer during VM startup.
> 
> -------------
> 
> PR: https://git.openjdk.java.net/jdk/pull/6442
>