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

[Yasumasa Suenaga]

Hi all,

This changes has been approved. But it was not passed JPRT.
It is caused by checking return value in HotSpotVirtualMachine#loadAgentLibrary().

I've fixed it and uploaded webrev. This changes has been passed JPRT. (Thanks David!)
Could you review again?

   hotspot: http://cr.openjdk.java.net/~ysuenaga/JDK-8164913/webrev.02/hotspot/
       jdk: http://cr.openjdk.java.net/~ysuenaga/JDK-8164913/webrev.02/jdk/


Thanks,

Yasumasa


On 2016/09/07 16:47, serguei.spitsyn at oracle.com wrote:
> On 9/7/16 00:45, Dmitry Samersoff wrote:
>> Serguei,
>>
>> I'm OK with the fix and OK to be listed as a reviewer.
>
> Thanks, Dmitry!
> Serguei
>>
>> -Dmitry
>>
>> On 2016-09-07 07:08, serguei.spitsyn at oracle.com wrote:
>>> Hi Dmitry,
>>>
>>> As a sponsor I'm going to push this fix if you are Ok with the fix.
>>> Please, let me know if you still have any concerns.
>>> Also, confirm if you are Ok to be in the list of reviewers.
>>>
>>>
>>> On 9/5/16 06:46, Dmitry Samersoff wrote:
>>>> Yasumasa,
>>>>
>>>> I'll look closely to the fix.
>>>>
>>>> Please, notice:
>>>>
>>>> 1. We typically avoid printing attach error messages on
>>>> the target VM side.
>>> Some message was already printed:
>>>
>>> 2410 // Agent_OnAttach executed so completion status is JNI_OK
>>> 2411 st->print_cr("%d", result);
>>> 2412 result = JNI_OK;
>>>
>>> It is just a replacement. :)
>>>
>>>
>>>> 2. We are in RDP1 for jdk9.
>>>>
>>>>     http://mail.openjdk.java.net/pipermail/jdk9-dev/2016-August/004777.html
>>> I've set the priority to P3, so it can be pushed to the jdk9/hs.
>>>
>>> Thanks,
>>> Serguei
>>>
>>>> -Dmitry
>>>>
>>>> On 2016-09-05 16:25, Yasumasa Suenaga wrote:
>>>>> PING: Could you review and sponsor it?
>>>>>
>>>>>>        http://cr.openjdk.java.net/~ysuenaga/JDK-8164913/webrev.01/
>>>>> Thanks,
>>>>>
>>>>> Yasumasa
>>>>>
>>>>>
>>>>> On 2016/09/01 12:47, Yasumasa Suenaga wrote:
>>>>>> Hi all,
>>>>>>
>>>>>> I think RDP1 has been started.
>>>>>> Cannot I fix this?
>>>>>>
>>>>>> 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 <http://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
>>>>>>
>>
>