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

[David Holmes]

Hi Yasumasa,

By chance we ran into this bug which I analysed yesterday:

https://bugs.openjdk.java.net/browse/JDK-8189390

We hit the assertion:

#  Internal Error (/open/src/hotspot/share/runtime/perfMemory.cpp:216), 
pid=17874, tid=17875
#  assert(_prologue != __null) failed: called before initialization
#

which is misleading because it can fail if called before initialization, 
or after PerfMemory::destroy has been called.

With your changes you no longer null out _prologue so the assertion 
would now not fail and we'd proceed to access the deleted memory region!

I'm unclear why you no longer clear all the fields set during 
initialization? But it seems to me that there are various checks of 
_prologue that should really be checking is_initialized() and/or 
is_destroyed() as a guard.

Thanks,
David

On 16/10/2017 11:25 PM, Yasumasa Suenaga wrote:
> PING:
> 
> Could you review it?
> 
>>    http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.05/
> 
> 
> Thanks,
> 
> Yasumasa
> 
> 
> On 2017/10/03 13:18, Yasumasa Suenaga wrote:
>> Hi all,
>>
>> I added gtest unit test case for this change in new webrev:
>>
>>    http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.05/
>>
>> Could you review it?
>>
>>
>> Thanks,
>>
>> Yasumasa
>>
>>
>>
>> 2017-09-27 0:01 GMT+09:00 Yasumasa Suenaga <yasuenag at gmail.com>:
>>> Hi all,
>>>
>>> I uploaded new webrev to be adapted to jdk10/hs:
>>>
>>>    http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.04/
>>>
>>>
>>> Thanks,
>>>
>>> Yasumasa
>>>
>>>
>>> On 2017/09/21 7:45, Yasumasa Suenaga wrote:
>>>>
>>>> PING:
>>>>
>>>> Have you checked this issue?
>>>>
>>>>>>     http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.03/
>>>>
>>>>
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>> On 2017/07/01 23:43, Yasumasa Suenaga wrote:
>>>>>
>>>>> PING:
>>>>>
>>>>> Have you checked this issue?
>>>>>
>>>>>
>>>>> Yasumasa
>>>>>
>>>>>
>>>>> On 2017/06/13 14:10, Yasumasa Suenaga wrote:
>>>>>>
>>>>>> Hi all,
>>>>>>
>>>>>> I want to discuss about JDK-8151815: Could not parse core image with
>>>>>> JSnap.
>>>>>>
>>>>>>
>>>>>> In last year, I found JSnap cannot parse coredump and I've sent 
>>>>>> review
>>>>>> request for it as JDK-8151815. However it has not been reviewed yet
>>>>>> [1].
>>>>>>
>>>>>> We've discussed about safety implementation, but we could not get
>>>>>> consensus.
>>>>>> IMHO all SA tools should be handled java processes and core images,
>>>>>> and PerfCounter value is useful. So I fix this issue.
>>>>>>
>>>>>> I uploaded new webrev for this issue. I think this patch is safety
>>>>>> because new flag PerfMemory::_destroyed guards double free, and all
>>>>>> members in PerfMemory is accessible (they are not munmap'ed)
>>>>>>
>>>>>>     http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.03/
>>>>>>
>>>>>>
>>>>>> Can you cooperate?
>>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Yasumasa
>>>>>>
>>>>>>
>>>>>> [1]
>>>>>> http://mail.openjdk.java.net/pipermail/serviceability-dev/2016-April/019480.html 
>>>>>>
>>>>>>
>>>