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

[David Holmes]

On 8/08/2016 10:26 AM, Yasumasa Suenaga wrote:
> 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.

I see - so we have to read memory element by memory element.

Okay - code seems okay.

Thanks,
David

> Thanks,
>
> Yasumasa
>
>
> 2016/08/08 8:52 "David Holmes" <david.holmes at oracle.com
> <mailto: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.hotspot.agent at 9-ea/ObjectReader.java:217)
>
>                 at
>         sun.jvm.hotspot.utilities.ObjectReader.readInstance(jdk.hotspot.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.iterateStaticFieldsInternal(jdk.hotspot.agent at 9-ea/InstanceKlass.java:572)
>
>                 at
>         sun.jvm.hotspot.oops.InstanceKlass.iterateStaticFields(jdk.hotspot.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/
>         <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
>
>