PING: RFR: JDK-8151815: Could not parse core image with JSnap.

[Dmitry Samersoff]

Yasumasa,

Yes. It's better.

Please place all _saved_* declarations together and add a comment
explaining what is the purpose of this variables.

-Dmitry


On 2016-04-13 15:20, Yasumasa Suenaga wrote:
> Hi all,
> 
> Could you review and sponsor it?
> 
>>    http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.01/
> 
> If it is not accepted, I think that we can add new field to PerfMemory
> for using in JSnap:
> -----------------------
> diff -r 4823056a5bbd src/share/vm/runtime/perfMemory.cpp
> --- a/src/share/vm/runtime/perfMemory.cpp    Tue Apr 12 09:08:48 2016 +0000
> +++ b/src/share/vm/runtime/perfMemory.cpp    Wed Apr 13 14:18:15 2016 +0900
> @@ -45,11 +45,16 @@
>                                              UINT_CHARS + 1;
>  
>  char*                    PerfMemory::_start = NULL;
> +char*                    PerfMemory::_saved_start = NULL;
>  char*                    PerfMemory::_end = NULL;
> +char*                    PerfMemory::_saved_end = NULL;
>  char*                    PerfMemory::_top = NULL;
> +char*                    PerfMemory::_saved_top = NULL;
>  size_t                   PerfMemory::_capacity = 0;
> +size_t                   PerfMemory::_saved_capacity = 0;
>  jint                     PerfMemory::_initialized = false;
>  PerfDataPrologue*        PerfMemory::_prologue = NULL;
> +PerfDataPrologue*        PerfMemory::_saved_prologue = NULL;
>  
>  void perfMemory_init() {
>  
> @@ -103,6 +108,8 @@
>  
>    // allocate PerfData memory region
>    create_memory_region(capacity);
> +  _saved_start = _start;
> +  _saved_capacity = _capacity;
>  
>    if (_start == NULL) {
>  
> @@ -132,8 +139,11 @@
>      }
>  
>      _prologue = (PerfDataPrologue *)_start;
> +    _saved_prologue = _prologue;
>      _end = _start + _capacity;
> +    _saved_end = _end;
>      _top = _start + sizeof(PerfDataPrologue);
> +    _saved_top = _top;
>    }
>  
>    assert(_prologue != NULL, "prologue pointer must be initialized");
> -----------------------
> 
> If it is better, I will upload a webrev.
> 
> 
> Thanks,
> 
> Yasumasa
> 
> 
> On 2016/04/06 12:42, Yasumasa Suenaga wrote:
>> Hi Dmitry,
>>
>> Thanks for your comment.
>>
>> I uploaded a new webrev. Could you review again?
>>    http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.01/
>>
>> On 2016/04/06 0:31, Dmitry Samersoff wrote:
>>> Yasumasa,
>>>
>>> 1. It's better to change JSnap code to produce meaningful error message
>>> instead of NPE.
>>
>> I added null check and set message to PerfMemory.java .
>>
>>
>>> 2. We should check that no other consumer of perf counters rely on the
>>> fact it's NULL after call to destroy(). I'm not sure that this part of
>>> the fix is not dangerous.
>>
>> I added new flag (_destroyed) in PerfMemory class.
>> This flag set true at PerfMemory::destroy().
>>
>> _start, _end, and more field which I removed from destroy() are
>> private member of
>> PerfMemory. I implemented that the getter functions of them check
>> _destroyed flag,
>> and returns same value before this change.
>>
>> So I think this change does not affect other place.
>>
>>
>> Thanks,
>>
>> Yasumasa
>>
>>
>>> -Dmitry
>>>
>>> On 2016-03-29 15:02, Yasumasa Suenaga wrote:
>>>> PING: Could you review it?
>>>>
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>> On 2016/03/22 21:24, Yasumasa Suenaga wrote:
>>>>> PING: Could you review it?
>>>>>
>>>>> Yasumasa
>>>>>
>>>>> 2016/03/14 23:39 "Yasumasa Suenaga" <yasuenag at gmail.com
>>>>> <mailto:yasuenag at gmail.com>>:
>>>>>
>>>>>      Hi all,
>>>>>
>>>>>      When I use `jhsdb jsnap` to get PerfCounter from core images, I
>>>>> encountered NPE:
>>>>>      -------------
>>>>>      Exception in thread "main" java.lang.NullPointerException
>>>>>               at sun.jvm.hotspot.tools.JSnap.run(JSnap.java:45)
>>>>>               at
>>>>> sun.jvm.hotspot.tools.Tool.startInternal(Tool.java:260)
>>>>>               at sun.jvm.hotspot.tools.Tool.start(Tool.java:223)
>>>>>               at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
>>>>>               at sun.jvm.hotspot.tools.JSnap.main(JSnap.java:67)
>>>>>               at
>>>>> sun.jvm.hotspot.SALauncher.runJSNAP(SALauncher.java:352)
>>>>>               at sun.jvm.hotspot.SALauncher.main(SALauncher.java:404)
>>>>>      -------------
>>>>>
>>>>>      PerfMemory::destroy() clears all members which are used in JSnap.
>>>>>      Thus NPE is occurred.
>>>>>
>>>>>      I uploaded webrev for this issue.
>>>>>      Could you review it?
>>>>>
>>>>>      http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.00/
>>>>>
>>>>>      I cannot access JPRT.
>>>>>      So I need a Sponsor.
>>>>>
>>>>>
>>>>>      Thanks,
>>>>>
>>>>>      Yasumasa
>>>>>
>>>
>>>


-- 
Dmitry Samersoff
Oracle Java development team, Saint Petersburg, Russia
* I would love to change the world, but they won't give me the sources.