RFR: 8350111: [PPC] AsyncGetCallTrace crashes when called while handling SIGTRAP [v2]

[Martin Doerr]

On Wed, 26 Feb 2025 10:57:31 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

>> With this change `JavaThread::pd_get_top_frame_for_profiling()` fails if the current thread is found to be `_thread_in_Java` but the CodeCache does not contain its pc.
>> 
>> This will prevent crashes as described by the JBS item.
>> 
>> The fix might be too conservative for situations where a thread doen't change its thread state when calling native code, e.g. using the Foreign Function & Memory API. The difficulty finding a less defensive fix is that one must detect if a valid pc can be found in the caller's ABI before constructing that frame.
>> 
>> Testing:
>> 
>> * DaCapo Tomcat with async-profiler on a fastdebug build.
>> * Tier 1-4 of hotspot and jdk on the main platforms and also on Linux/PPC64le and AIX.
>
> Richard Reingruber has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - A frame isn't safe_for_sender if sender_pc() returns null
>  - Revert first fix
>    
>    This reverts commit c4b81e2dc5a854efde8475d09b33b8f53dde987d.

Thanks! This solution looks much better!

src/hotspot/cpu/ppc/frame_ppc.cpp line 200:

> 198:   if (sender_pc() == nullptr) {
> 199:     // Likely the return pc was not yet stored to stack.  We rather discard this
> 200:     // sample also because we would hit an assertion in frame::setup().  We can

Double-whitespaces seem to be uncommon.

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Marked as reviewed by mdoerr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23641#pullrequestreview-2644462134
PR Review Comment: https://git.openjdk.org/jdk/pull/23641#discussion_r1971574689