RFR: 8372039: post_sampled_object_alloc is called while lock is handled [v5]

[Serguei Spitsyn]

On Tue, 2 Dec 2025 21:09:11 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> The AOT allocates objects while holding lock. The jvmti events can't be posted in such case. The allocation sampling might be just temporary disabled while AOT objects are allocated. 
>> 
>> I prefer to disable jvmti events for allocation only, not for AOT globally. If there are more events should be generated during AOT initialization, we might want to preserve them and post after initialization is completed. 
>> 
>> The existing failure could be reproduced by running tests with jvmti stress agent and ZGC enabled. Like
>> make run-test JTREG_JVMTI_STRESS_AGENT=debugger=true TEST=gc/z/TestGarbageCollectorMXBean.java
>> 
>> Note: 
>> I prelaced NoJvmtiVMObjectAllocMark, it was not used. Also it was incorrect. The 
>> NoJvmtiEventsMark should be set even if jvmti events are not enable for this thread. Since jvmti events might be enabled just in the middle of the mark.
>
> Leonid Mesnik has updated the pull request incrementally with seven additional commits since the last revision:
> 
>  - Apply suggestion from @alexmenkov
>    
>    Co-authored-by: Alex Menkov <alexey.menkov at oracle.com>
>  - Apply suggestion from @alexmenkov
>    
>    Co-authored-by: Alex Menkov <alexey.menkov at oracle.com>
>  - Apply suggestion from @alexmenkov
>    
>    Co-authored-by: Alex Menkov <alexey.menkov at oracle.com>
>  - Update test/hotspot/jtreg/serviceability/jvmti/events/SampledObjectAlloc/SamplingDuringInit/libSamplingDuringInit.cpp
>    
>    Co-authored-by: Alex Menkov <alexey.menkov at oracle.com>
>  - Update test/hotspot/jtreg/serviceability/jvmti/events/SampledObjectAlloc/SamplingDuringInit/SamplingDuringInit.java
>    
>    Co-authored-by: Alex Menkov <alexey.menkov at oracle.com>
>  - Update src/hotspot/share/runtime/javaThread.hpp
>    
>    Co-authored-by: Alex Menkov <alexey.menkov at oracle.com>
>  - Update src/hotspot/share/runtime/javaThread.cpp
>    
>    Co-authored-by: Alex Menkov <alexey.menkov at oracle.com>

The fix looks good in general. I've requested a minor test update though.

test/hotspot/jtreg/serviceability/jvmti/events/SampledObjectAlloc/SamplingDuringInit/libSamplingDuringInit.cpp line 32:

> 30: SampledObjectAlloc(jvmtiEnv *jvmti, JNIEnv* jni, jthread thread, jobject object, jclass object_klass, jlong size) {
> 31:   LOG("Sampled object\n");
> 32: }

I'd suggest to increment a counter here. Then check it at the end and fail if it is not 0.

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PR Review: https://git.openjdk.org/jdk/pull/28544#pullrequestreview-3532263502
PR Review Comment: https://git.openjdk.org/jdk/pull/28544#discussion_r2582904026