[PATCH RFC 0/2] Add linux/ppc64 support for Hotspot serviceability agent to read core files

[Volker Simonis]

Hi Maynard,

I'm currently looking at your changes. At first glance they look good.

I could open a simple core file which contained both, interpreted and
compiled frames:

$ jstack ./images/j2sdk-image/bin/java core.7034
...
Thread 7035: (state = IN_VM)
 - sun.misc.Unsafe.putAddress(long, long) @bci=0 (Interpreted frame)
 - Crash.crashIt(sun.misc.Unsafe, int) @bci=10, line=8 (Interpreted frame)
 - Crash.doIt() @bci=45, line=23 (Compiled frame)
 - sun.reflect.NativeMethodAccessorImpl.invoke0(java.lang.reflect.Method,
java.lang.Object, java.lang.Object[]) @bci=0 (Interpreted frame)
 - sun.reflect.NativeMethodAccessorImpl.invoke(java.lang.Object,
java.lang.Object[]) @bci=100, line=62 (Interpreted frame)
 - sun.reflect.DelegatingMethodAccessorImpl.invoke(java.lang.Object,
java.lang.Object[]) @bci=6, line=43 (Interpreted frame)
 - java.lang.reflect.Method.invoke(java.lang.Object,
java.lang.Object[]) @bci=56, line=498 (Interpreted frame)
 - Crash.main(java.lang.String[]) @bci=32, line=31 (Interpreted frame)

The one thing that doesn't currently work is "jstack -m" (i.e. "mixed
mode" for java and native frames). Are you aware of this?

Regarding your "test.java" example - how do you use it?

If I just attach with jstack to the Java process which runs
"test.java" I get the correct stack trace of all threads. But I think
that's actual no SA-functionality but a VM-feature (the same that can
be triggered by sending kill -SIGQUIT to  java process).

If I attach with "jstack -F" I see the problems you mentioned. First I
didn't saw any frame at all which confused me but then I also saw the
two cases mentioned by you. I'll need to have a closer look what
happens.

Regards,
Volker



On Fri, Nov 14, 2014 at 7:09 PM, Maynard Johnson <maynardj at us.ibm.com> wrote:
> When Hotspot SA tools jmap, jstack, and jsadebugd are run against a core file, they fail with the following runtime exception:
>
>      OS/CPU combination linux/ppc64 not yet supported
>
> I will post a patch set that adds this support.  The patch set consists of the following patches:
>
> PATCH 1/2: Updates to non-Java files to support linux/ppc64 Hotspot SA with core files
>
> PATCH 2/2: New PPC64 class files (and updates to generic files) to support linux/ppc64 Hotspot SA with core files
>
> These two patches apply cleanly to a November 13 pull of the jdk9-dev upstream sources.
>
> ------------
> Open issues:
> ------------
>   1) The jstack tool does not print a stack entry for the 'main()' method of the Java
>      workload (attached) under test.  For example:
>
>      (Note:  Addresses and method signatures elided for brevity.)
>
>        Thread 24358: (state = IN_JAVA, current Java SP = null
>        )
>         - java.lang.String.getChars(...) @bci=58, line=814, pc=..., Method*=... (Compiled frame; ... imprecise)
>         - test.run_test() @bci=80, line=33, pc=..., Method*=... (Compiled frame)
>      ==> (Expect an entry for test.main() here)
>
>   2) The jstack tool sometimes prints what appears to be two complete stacks for the Java workload. For example:
>
>        Thread 24779: (state = IN_JAVA, current Java SP = null
>        )
>         - java.lang.String.getChars(...) @bci=58, line=814, pc=..., Method*=... (Compiled frame; ... imprecise)
>         - test.run_test() @bci=80, line=33, pc=..., Method*=... (Compiled frame)
>         - test.get_my_chars(...) @bci=39, line=15, pc=..., Method*=... (Compiled frame)
>         - test.run_test() @bci=92, line=34, pc=..., Method*=... (Compiled frame)
>
>        Again, the 'test.main' method is missing, but there's also the anomaly of the
>        test.run_test' method showing up twice in the stack, implying that it is called
>        by 'test.get_my_chars' at line 15.  But that that is not accurate. In fact, run_test
>        does call String.getChars at line 33 *and* it calls test.get_my_chars at line 34 --
>        but these are totally distinct call graphs.  Somehow, we are seeing these two distinct
>        stacks in the core file, which seems impossible.
>
> ---------
>
> Any help offered on these two open issues would be greatly appreciated.
>
> -Maynard