RFR: JDK-8163272: jhsdb jinfo cannot show system properties

[Yasumasa Suenaga]

Hi David,

To get properties from memory, SA have to know memory layout.
SA is used for attaching to live process/core image. So we cannot execute
Java API.

Thanks,

Yasumasa

2016/08/08 8:52 "David Holmes" <david.holmes at oracle.com>:

> Hi Yasumasa,
>
> On 5/08/2016 9:59 PM, Yasumasa Suenaga wrote:
>
>> Hi all,
>>
>> I tried to get system properties via "jhsdb jinfo".
>> However, it did not work as below:
>>
>> ----------------
>> $ /usr/local/jdk-9/bin/jhsdb jinfo --pid 1002
>> Attaching to process ID 1002, please wait...
>> Debugger attached successfully.
>> Server compiler detected.
>> JVM version is 9-ea+129
>> Java System Properties:
>>
>> java.lang.NullPointerException
>>         at
>> sun.jvm.hotspot.utilities.ObjectReader.getHashtable(jdk.hots
>> pot.agent at 9-ea/ObjectReader.java:217)
>>
>>         at
>> sun.jvm.hotspot.utilities.ObjectReader.readInstance(jdk.hots
>> pot.agent at 9-ea/ObjectReader.java:247)
>>
>>         at
>> sun.jvm.hotspot.utilities.ObjectReader.readObject(jdk.hotspot.agent at 9-ea
>> /ObjectReader.java:105)
>>
>>         at
>> sun.jvm.hotspot.runtime.VM$2.doOop(jdk.hotspot.agent at 9-ea/VM.java:940)
>>         at
>> sun.jvm.hotspot.oops.InstanceKlass.visitField(jdk.hotspot.agent at 9-ea
>> /InstanceKlass.java:872)
>>
>>         at
>> sun.jvm.hotspot.oops.InstanceKlass.iterateStaticFieldsIntern
>> al(jdk.hotspot.agent at 9-ea/InstanceKlass.java:572)
>>
>>         at
>> sun.jvm.hotspot.oops.InstanceKlass.iterateStaticFields(jdk.h
>> otspot.agent at 9-ea/InstanceKlass.java:560)
>>
>>         at
>> sun.jvm.hotspot.runtime.VM.readSystemProperties(jdk.hotspot.agent at 9-ea
>> /VM.java:935)
>>
>>                :
>> System Properties info not available!
>> ----------------
>> * If you want to see all stack, please see JBS.
>>
>>
>> I think this is caused by JDK-8029891.
>> JDK-8029891 changes that j.u.Properties stores properties to
>> j.u.c.ConcurrentHashMap.
>> ObjectReader should be adapted to this change.
>>
>> I uploaded webrev. Could you review it?
>>
>>   http://cr.openjdk.java.net/~ysuenaga/JDK-8163272/webrev.00/
>>
>
> I'm not very familiar with how SA operates here so this could be a stupid
> question, but why do we need to know exactly how Properties are implemented
> instead of just using the public API to access them and read/write them ??
>
> Thanks,
> David
>
> I'm jdk 9 commiter, but I cannot access JPRT.
>> So I need a sponsor.
>>
>>
>> Thanks,
>>
>> Yasumasa
>>
>>
>>
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