RFR: 8339772: serviceability/sa/TestJhsdbJstackUpcall.java fails on Linux ppc64le

[Martin Doerr]

On Thu, 19 Sep 2024 14:52:07 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> The SA model of the UpcallStub doesn't work reliably on PPC64. We can use the Backchain which works for all Power Architecture 64-Bit ELF ABI compliant frames. (The backtrace should stop when hitting a non-compliant frame which can occur with some compiler options. Also see comment in JBS issue.)
> Note that this enables walking the native frames which is possible on PPC64, but not on some other platforms due to missing backlinks.
> 
> "test/hotspot/jtreg/serviceability" tests have passed with this PR.

> I'm not sure whether this PR is correct - if the app has several call stacks which do not compliant the ABI, this PR would not work. See [#20789 (comment)](https://github.com/openjdk/jdk/pull/20789#issuecomment-2324964613) for details.
> 
> It is better to use JavaFrameAnchor like other platforms if we can.

We don't support frames which don't follow the ABI. I think stopping the backtrace immediately is an appropriate reaction. Other debuggers like GDB would do the same. Nevertheless, I couldn't spot any bug in your new code. So, I've debugged the issue and found [JDK-8340657](https://bugs.openjdk.org/browse/JDK-8340657) which causes the problem.

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PR Comment: https://git.openjdk.org/jdk/pull/21092#issuecomment-2368595882