RFR: JDK-8164913: JVMTI.agent_load dcmd should show useful error message

[serguei.spitsyn at oracle.com]

Hi Yasumasa,

Please, find my comment below.


On 9/6/16 06:06, Yasumasa Suenaga wrote:
> Hi David,
>
>> Is this something specific to code added in 9? If so that is 
>> motivation as we should not have a new feature with known bugs if we 
>> can avoid it. But if this already exists in JDK 8 and is a long 
>> standing "bug" ...
>
> The change for jvmtiExport.cpp can apply jdk8u:
>
> http://hg.openjdk.java.net/jdk8u/jdk8u-dev/hotspot/file/d55ea2916525/src/share/vm/prims/jvmtiExport.cpp#l2270
>
> I think HotSpot in jdk8u ignores exception and return JNI_OK even if 
> Agent_OnAttach() fails.
> OTOH, the change for diagnosticCommand.cpp affects jdk9 only.
>
>
> Thanks,
>
> Yasumasa
>
>
> On 2016/09/06 9:54, David Holmes wrote:
>> Hi Yasumasa,
>>
>> On 1/09/2016 1:47 PM, Yasumasa Suenaga wrote:
>>> Hi all,
>>>
>>> I think RDP1 has been started.
>>> Cannot I fix this?
>>
>> "P4-P5 bugs should, in general, be left to future releases unless they
>> only affect documentation, demos, or tests, in which case they should be
>> identified as such with the "noreg-doc", "noreg-demo", and "noreg-self"
>> labels, respectively." [1]
>>
>> This is due to the need to stabilize changes as we head towards GA.
>>
>> I think you would have to justify why this should be a P3 rather than 
>> P4 issue.


This needs to be answered as well.


Thanks,
Serguei


>> Is this something specific to code added in 9? If so that is 
>> motivation as we should not have a new feature with known bugs if we 
>> can avoid it. But if this already exists in JDK 8 and is a long 
>> standing "bug" ...
>>
>> David
>>
>> [1] 
>> http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-August/004777.html
>>
>>
>>> This problem is that jcmd shows incorrect status when JVMTI agent 
>>> cannot
>>> be attached.
>>> I think this problem should be fixed in 9 GA.
>>> The users who want.to attach JVMTI agent want to know
>>> whether it succeed.
>>>
>>> Yasumasa
>>>
>>>
>>> 2016/08/29 15:42 "Yasumasa Suenaga" <yasuenag at gmail.com
>>> <mailto:yasuenag at gmail.com>>:
>>>
>>>         This comment no longer matches the code and should be deleted:
>>>
>>>         2412       // Agent_OnAttach executed so completion status 
>>> is JNI_OK
>>>         2413       st->print_cr("return code: %d", result);
>>>
>>>
>>>     Thanks David!
>>>     I removed it in new webrev.
>>>
>>> http://cr.openjdk.java.net/~ysuenaga/JDK-8164913/webrev.01/
>>> <http://cr.openjdk.java.net/~ysuenaga/JDK-8164913/webrev.01/>
>>>
>>>
>>>     Yasumasa
>>>
>>>
>>>     On 2016/08/29 12:59, David Holmes wrote:
>>>
>>>         Hi Yasumasa,
>>>
>>>         On 28/08/2016 10:47 PM, Yasumasa Suenaga wrote:
>>>
>>>             Hi all,
>>>
>>>             If we try to attach invalid JVMTI agent via 
>>> JVMTI.agent_load
>>>             dcmd, we
>>>             will get
>>>             "Command executed successfully". However, it implies 
>>> error in
>>>             JVMTIAgentLoadDCmd.
>>>
>>>             This message is from JCmd.java when jcmd does not receive
>>>             output from
>>>             target VM.
>>>             So we should send error message from JVMTIAgentLoadDCmd.
>>>
>>>             I uploaded a webrev for it. Could you review it?
>>>
>>>
>>> http://cr.openjdk.java.net/~ysuenaga/JDK-8164913/webrev.00/
>>> <http://cr.openjdk.java.net/~ysuenaga/JDK-8164913/webrev.00/>
>>>
>>>
>>>         This seems reasonable.
>>>
>>>         src/share/vm/prims/jvmtiExport.cpp
>>>
>>>         This comment no longer matches the code and should be deleted:
>>>
>>>         2412       // Agent_OnAttach executed so completion status 
>>> is JNI_OK
>>>         2413       st->print_cr("return code: %d", result);
>>>
>>>         Thanks,
>>>         David
>>>
>>>             I cannot access JPRT.
>>>             So I need a sponsor.
>>>
>>>
>>>             Thanks,
>>>
>>>             Yasumasa
>>>