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

David Holmes david.holmes at oracle.com
Wed Oct 18 04:44:58 UTC 2017 

On 18/10/2017 2:27 PM, Yasumasa Suenaga wrote:
> Hi David,
> 
> 2017-10-18 12:55 GMT+09:00 David Holmes <david.holmes at oracle.com>:
>> On 18/10/2017 12:37 PM, Yasumasa Suenaga wrote:
>>>
>>> Hi David,
>>>
>>>> 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!
>>>
>>>
>>> On Linux, PerfMemory::delete_memory_region() does not call munmap()
>>> for PerfMemory.
>>
>>
>> Perhaps not but there are still other actions that happen and the point is
>> we should not be able to continue to use PerfMemory once it has been
>> destroyed (even if the destruction is only logical).
> 
> I received same comment from Dmitry in the past, but we couldn't
> decide how should we do.
> 
>    http://mail.openjdk.java.net/pipermail/serviceability-dev/2016-May/019728.html
> 
> In that discussion, I uploaded another webrev which adds other fields for JSnap.
> Is it suitable?
> 
>    http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.02/

I don't think we need the extra fields, just ensure the existing ones 
can't be accessed (other than by the tools) after destroy is called.

> 
>>>> I'm unclear why you no longer clear all the fields set during
>>>> initialization?
>>>
>>>
>>> PerfMemory.java in jdk.hotspot.agent needs these field values.
>>> `jhsdb jsnap --core` is failed if they are cleared.
>>
>>
>> I'm not familiar with these tools. When do we produce a core file after
>> calling PerfMemory::destroy ?
> 
> PerfMemory::destroy() is called before aborting.

Ah - right. I assume we need to close off the perfdata file before we abort.

Thanks,
David

> -----------------------
> #0  perfMemory_exit ()
>      at /usr/src/debug/java-1.8.0-openjdk-1.8.0.144-7.b01.fc26.x86_64/openjdk/hotspot/src/share/vm/runtime/perfMemory.cpp:80
> #1  0x00007f99b091c949 in os::shutdown ()
>      at /usr/src/debug/java-1.8.0-openjdk-1.8.0.144-7.b01.fc26.x86_64/openjdk/hotspot/src/os/linux/vm/os_linux.cpp:1483
> #2  0x00007f99b091c980 in os::abort (dump_core=<optimized out>)
>      at /usr/src/debug/java-1.8.0-openjdk-1.8.0.144-7.b01.fc26.x86_64/openjdk/hotspot/src/os/linux/vm/os_linux.cpp:1503
> #3  0x00007f99b0b689c3 in VMError::report_and_die (
>      this=this at entry=0x7ffcacf40b50)
>      at /usr/src/debug/java-1.8.0-openjdk-1.8.0.144-7.b01.fc26.x86_64/openjdk/hotspot/src/share/vm/utilities/vmError.cpp:1060
> #4  0x00007f99b0926f04 in JVM_handle_linux_signal (sig=sig at entry=11,
>      info=info at entry=0x7ffcacf40df0, ucVoid=ucVoid at entry=0x7ffcacf40cc0,
>      abort_if_unrecognized=abort_if_unrecognized at entry=1)
>      at /usr/src/debug/java-1.8.0-openjdk-1.8.0.144-7.b01.fc26.x86_64/openjdk/hotspot/src/os_cpu/linux_x86/vm/os_linux_x86.cpp:541
> -----------------------
> 
> 
> Thanks,
> 
> Yasumasa
> 
> 
>>>> 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.
>>>
>>>
>>> Should I change all assertions for _prologue?
>>
>>
>> Assertions and direct guards. Checking _prologue is a placeholder for the
>> real check.
>>
>>
>> Thanks,
>> David
>>
>>
>>>
>>> Thanks,
>>>
>>> Yasumasa
>>>
>>>
>>> 2017-10-18 10:53 GMT+09:00 David Holmes <david.holmes at oracle.com>:
>>>>
>>>> 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
>>>>>>>>>>
>>>>>>>
>>>>
>>

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