RFR: 8370176: Mixed mode jhsdb jstack cannot unwind call stack with -Xcomp [v2]

[Yasumasa Suenaga]

On Thu, 23 Oct 2025 06:14:53 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Can you share .jtr file?
>
> Sure. This is what I got on my amd64 machine:
> 
> ```$ make test TEST="serviceability/sa/TestJhsdbJstackMixedWithXComp.java"```
> 
> [TestJhsdbJstackMixedWithXComp.jtr.txt](https://github.com/user-attachments/files/23091141/TestJhsdbJstackMixedWithXComp.jtr.txt)

@RealFYang Thank you for sharing it!

I think it might be caused by binary difference, it is not caused by this PR at least. So I think we can go forward this PR, make sence?

Your .jtr file implies stack unwinding was failed from the function by libc in following:

----------------- 2310034 -----------------
"SteadyStateThread" #39 prio=5 tid=0x00007fd2600358a0 nid=2310034 waiting for monitor entry [0x00007fd2351f4000]
   java.lang.Thread.State: BLOCKED (on object monitor)
   JavaThread state: _thread_blocked
0x00007fd267930f16      __futex_abstimed_wait_common + 0xc6
----------------- 2310033 -----------------
"ForkJoinPool-1-worker-2" #38 daemon prio=5 tid=0x00007fd1ec006600 nid=2310033 runnable [0x00007fd2352f5000]
   java.lang.Thread.State: RUNNABLE
   JavaThread state: _thread_in_native
0x00007fd26797a545      __clock_nanosleep + 0x65
0x00007fd26797ee53      __GI___nanosleep + 0x13


Native stack unwinding on Linux AMD64 depends on DWARF (in AArch64, it depends on FP (x29) yet).
I downloaded and checked libc.so.6 in libc6-udeb_2.41-12_amd64.udeb, it has `.eh_frame` section which would be used by `DwarfParser`, but it does not have any symbols, and not have `.gnu_debuglink` ELF section. OTOH Fedora 43 which I confirmed to work has both symbols and `.gnu_debuglink`.

They are used for symbol resolution, not stack unwinding. However other difference(s) in binary might affect statck unwinding. Thus I think it is not a problem caused by this PR.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27885#discussion_r2454170838