[lworld] RFR: 8368002: [lworld] Crash in ThawBase::remove_top_compiled_frame_from_chunk [v2]

[Coleen Phillimore]

On Mon, 22 Sep 2025 17:22:48 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> Please review this small fix. When thawing in the fast path, the top frame could be a runtime stub due to preempting on monitorenter. In the changes for JDK-8336845 I missed this, leading to a crash when dereferencing the nullptr returned by `f.cb()->as_nmethod_or_null()` in `ThawBase::remove_top_compiled_frame_from_chunk`.
>> 
>> I was able to reproduce the failure locally and verified it is now fixed. I did run into a pre-existing crash with Jetty (filed JDK-8368099). I also run all tests in java/lang/Thread/virtual stressing this path, tests Fuzz.java and TestVirtualThreads.java, plus extra mach5 tier testing.
>> 
>> Thanks,
>> Patricio
>
> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove frames_size parameter and code duplication from remove_scalarized_frames

src/hotspot/share/runtime/continuationFreezeThaw.cpp line 2076:

> 2074: 
> 2075: int ThawBase::remove_scalarized_frames(StackChunkFrameStream<ChunkFrames::CompiledOnly>& f, stackChunkOop chunk, int &argsize) {
> 2076:   DEBUG_ONLY(intptr_t* const chunk_sp = chunk->start_address() + chunk->sp();)

Can you remove the 'chunk' parameter too?

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PR Review Comment: https://git.openjdk.org/valhalla/pull/1603#discussion_r2369700392