RFR: JDK-8174994: SA: clhsdb printmdo throws WrongTypeException when attached to a process with CDS

Jini George jini.george at oracle.com
Tue Apr 24 09:03:23 UTC 2018


The webrev including the check for the "|" at the beginning of the 
core_pattern file is at:


This webrev also includes a fix for a latent bug on MacOSX, where 
corefile debugging was failing due to SA trying to read in the incorrect 
mangled symbol name for "Arguments::SharedArchivePath". Clang seems to 
have prefixed an extra '_' to change the mangled name from 
'_ZN9Arguments17SharedArchivePathE' to 
'__ZN9Arguments17SharedArchivePathE' for MachO files. This fix for this 
is in src/jdk.hotspot.agent/macosx/native/libsaproc/ps_core.c.

The difference between the earlier patch and this one can be seen at:


Thank you,

On 4/18/2018 10:37 PM, Jini George wrote:
> I agree with the need of testing as much as we can. I could do something 
> on the lines of how other debuggers like LLDB test: if we can't find the 
> core file location, check for "|" at the beginning of a line in the 
> /proc/sys/kernel/core_pattern file -- and fail with a message stating 
> that the system is using a crash reporting tool.
> Thank you,
> Jini.
> On 4/18/2018 12:40 PM, David Holmes wrote:
>> My 2c ...
>> We have to have tests that can test core file attaching capability - 
>> else we don't know it works. So we have to try and generate a core file.
>> But, we have to expect that in many cases no core file will be 
>> generated even if the hs-err file claims it was. For example my 
>> primary local testing system never generates core files even though it 
>> claims to:
>> # Core dump will be written. Default location: Core dumps may be 
>> processed with "/usr/share/apport/apport %p %s %c" (or dumping to /
>> export/users/dh198349/valhalla/repos/valhalla-dev/open/test/jdk/core.29848) 
>> apport isn't even installed, even though core_pattern lists it.
>> Cheers,
>> David
>> On 18/04/2018 4:36 PM, Yasumasa Suenaga wrote:
>>> 2018-04-18 15:05 GMT+09:00 Jini George <jini.george at oracle.com>:
>>>> Thank you very much, Yasumasa, for pointing this out. You are right 
>>>> -- this
>>>> would fail in the Linux systems if systemd-coredump is enabled.
>>>> I plan to file an enhancement request to address this issue (wrt
>>>> systemd-coredump) separately since this would apply to other coredump
>>>> generating test cases also like:
>>>> test/hotspot/jtreg/compiler/ciReplay/TestSAServer.java.
>>> I agree with you, but...
>>>>  From what i can gather, i think we might be able to at least partially
>>>> address this by using
>>>> coredumptl -o <desired_core_path> dump <pid of the crashed process>
>>>> in the test cases, provided the kernel.core_pattern variable is not 
>>>> set to
>>>> "|/bin/false".
>>>> Let me know if you are not OK with this.
>>> IMHO it is not good.
>>> Some Linux distros use other coredump collector. For example, RHEL 6
>>> uses ABRT, Ubuntu uses Apport, Fedora uses systemd-coredump.
>>> Hence I think we should disable all tests which requires core images
>>> for Linux like a Windows platform.
>>> Thanks,
>>> Yasumasa
>>>> Thank you,
>>>> Jini.
>>>> On 4/14/2018 7:39 PM, Yasumasa Suenaga wrote:
>>>>> Hi Jini,
>>>>> ClhsdbCDSCore.java:
>>>>>     Can this test work on modern Linux?
>>>>>     AFAIK modern Linux contains systemd-coredump to gather core 
>>>>> images. So
>>>>> I concern ClhsdbCDSCore.java fails in the future.
>>>>> Thanks,
>>>>> Yasumasa
>>>>> On 2018/04/12 13:21, Jini George wrote:
>>>>>> Ping: Gentle reminder !
>>>>>> Thanks,
>>>>>> Jini.
>>>>>> On 4/6/2018 9:51 PM, Jini George wrote:
>>>>>>> Hello!
>>>>>>> Requesting reviews for: 
>>>>>>> https://bugs.openjdk.java.net/browse/JDK-8174994
>>>>>>> Webrev: http://cr.openjdk.java.net/~jgeorge/8174994/webrev.00/
>>>>>>> While trying to identify the type given an address, a 
>>>>>>> WrongTypeException
>>>>>>> was getting thrown with various clhsdb commands (like printmdo, 
>>>>>>> jstack,
>>>>>>> etc). This was since SA tries to map an address to a hotspot C++ 
>>>>>>> type by
>>>>>>> comparing the vtable address to the vtable address values of known
>>>>>>> types. With CDS, since the vtables are copied over for the Metadata
>>>>>>> classes, the vtable addresses themselves don't match (though, of 
>>>>>>> course,
>>>>>>> the contents will), and SA errors out.
>>>>>>> The fix has been implemented by making changes to read in the md 
>>>>>>> region
>>>>>>> (consisting of the c++ vtables) of the CDS archive in SA, and 
>>>>>>> mapping
>>>>>>> the vtable addresses to the corresponding metadata type 
>>>>>>> (ConstantPool,
>>>>>>> InstanceKlass, InstanceClassLoaderKlass, InstanceMirrorKlass,
>>>>>>> InstanceRefKlass, Method, ObjArrayKlass, TypeArrayKlass).
>>>>>>> For corefiles, an additional modification has been done to have the
>>>>>>> replicated FileMapHeader structure (from
>>>>>>> src/hotspot/share/memory/filemap.hpp, which is replicated in SA in
>>>>>>> ps_core.c), to be in sync with the corresponding definition in
>>>>>>> src/hotspot/share/memory/filemap.hpp.
>>>>>>> Test cases to test both live and corefile debugging are being 
>>>>>>> added with
>>>>>>> this. These and other SA tests pass on Mach5.
>>>>>>> Thanks,
>>>>>>> Jini.

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