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
