RFR: JDK-8187597: WrongTypeException is occurred at CLHSDB jstack after JDK-8186837

[Chris Plummer]

Hi Yasumasa,

Ok, I see now that CIntegerField is just an interface, so it's up to a 
class to implement getValue() to fetch the field. I'm a bit unclear on 
how that part works, but from responses by others, it seems this is ok.

I've run all the tests I can find that use jstack or jhsdb, and the 
assert was not triggered. Probably need to have a NMethod on the stack 
to trigger the code you are fixing.

thanks,

Chris

On 9/17/17 1:13 AM, Yasumasa Suenaga wrote:
> Hi Chris,
>
> I've tested this issue on Fedora 26 x86_64.
> I think we can sue CIntegerField at this point because CIntegerField 
> is not specialized for various int size [1].
> In fact, CIntegerField had been used at this point [2], and HSDB 
> worked fine.
>
>
> Thanks,
>
> Yasumasa
>
>
> [1] 
> http://hg.openjdk.java.net/jdk10/master/file/fd36993f7bf5/src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/types/CIntegerField.java#l29
> [2] http://hg.openjdk.java.net/jdk10/master/rev/cbfdbefc6ea3
>
>
> On 2017/09/17 3:58, Chris Plummer wrote:
>> Hi Yasumasa,
>>
>> Is this on a 32-bit system? I don't see how you could otherwise call 
>> getCIntegerField() on a long type. jlong is always 64-bit and long is 
>> (generally) 32-bit on 32-bit systems, and 64-bit on 64-bit systems, 
>> at least that seems to be the case with linux.
>>
>>  From what I can see, _stack_traversal_mark is now the only long type 
>> in vmStructs.cpp. I don't know that we have a mechanism to safely 
>> fetch it on both 32-bit and 64-bit systems.
>>
>> _stack_traversal_mark seems to be a long because _traversals is also 
>> a long.
>>
>>      static long      _traversals;                   // Stack scan 
>> count, also sweep ID.
>>
>> This too might be considered a bug. I'm not sure why you would want 
>> the size of this field to vary between 32-bit and 64-bit systems 
>> (adding compiler-dev to help answer that).
>>
>> So, while I would agree that your fix is generally in the right 
>> direction, I think we first need to revisit the use of long for these 
>> fields. If they can be changed to an int, then your fix is correct 
>> (pending the changes to int). If not, then maybe we need 
>> getCLongField() support.
>>
>> And lastly, we really should have a test to detect this bug. Maybe we 
>> already do, and it is failing but is going unnoticed for some reason. 
>> I'll try to look into that some more on Monday.
>>
>> thanks,
>>
>> Chris
>>
>> On 9/16/17 5:20 AM, Yasumasa Suenaga wrote:
>>> Hi all,
>>>
>>> I tried to get thread dump via jstack command on CLHSDB. But it was 
>>> failed as below:
>>>
>>> ```
>>> Caused by: sun.jvm.hotspot.types.WrongTypeException: field 
>>> "_stack_traversal_mark" in type nmethod is not of type jlong, but 
>>> instead of type long
>>>         at 
>>> jdk.hotspot.agent/sun.jvm.hotspot.types.basic.BasicType.getField(BasicType.java:206)
>>>         at 
>>> jdk.hotspot.agent/sun.jvm.hotspot.types.basic.BasicType.getField(BasicType.java:212)
>>>         at 
>>> jdk.hotspot.agent/sun.jvm.hotspot.types.basic.BasicType.getJLongField(BasicType.java:249)
>>>         at 
>>> jdk.hotspot.agent/sun.jvm.hotspot.code.NMethod.initialize(NMethod.java:108)
>>>         at 
>>> jdk.hotspot.agent/sun.jvm.hotspot.code.NMethod.access$000(NMethod.java:35)
>>>         at 
>>> jdk.hotspot.agent/sun.jvm.hotspot.code.NMethod$1.update(NMethod.java:81) 
>>>
>>>         at 
>>> jdk.hotspot.agent/sun.jvm.hotspot.runtime.VM.registerVMInitializedObserver(VM.java:451)
>>>         at 
>>> jdk.hotspot.agent/sun.jvm.hotspot.code.NMethod.<clinit>(NMethod.java:79)
>>>         ... 23 more
>>> ```
>>>
>>> I think this exception is caused by JDK-8186837.
>>> This changeset has changed the type of 
>>> `nmethod::_stack_traversal_mark` to `long` from `jlong`.
>>>
>>> SA should follow this change.
>>>
>>> I uploaded a webrev for this issue. This webrev is generated from 
>>> consolidated repo (jdk10/master).
>>> Could you review it?
>>>
>>>   http://cr.openjdk.java.net/~ysuenaga/JDK-8187597/webrev.00/
>>>
>>>
>>> I cannot access JPRT. So I need reviewer.
>>>
>>>
>>> Thanks,
>>>
>>> Yasumasa
>>>
>>
>>