RFR: 8370198: Test gc/arguments/TestShrinkHeapInSteps.java crashed: assert(left >= right) failed: avoid underflow

[Albert Mingkun Yang]

On Wed, 19 Nov 2025 15:39:27 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Add an early-return for outside-heap address in `CollectedHeap::is_in` API.
> 
> While investigating this failure (JDK-8370198), I realized that some java-threads (compiler-threads) in `native` state can invoke `CollectedHeap` APIs. Since heap-resizing occurs inside safepoint but java-threads in `native` state just ignore safepoint, I have added some assert to catch such dangerous uses, where the return value might not be stable.
> 
> Test: tie1-5; can't reproduce the JDK-8370198 with or without this patch for >8000 runs.

After some offline discussion with Stefan, it's suggested that `CollectedHeap::is_in` should probably require callers to be in good state (e.g. not java-threads-in-native).

After removing the asserts in `MacroAssembler::set_narrow_klass`, I don't any crashes with placing such state-verification at the beginning of `is_in`. Therefore, it's probably best to make the assumption explicit (as a precondition).

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PR Comment: https://git.openjdk.org/jdk/pull/28393#issuecomment-3611267941