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

[Chris Plummer]

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
>