RFR: 8311177: Switching to interpreter only mode in carrier thread can lead to crashes [v3]

[Alex Menkov]

On Fri, 31 May 2024 23:55:20 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> Please, review the following `interp-only` issue related to carrier threads.
>> There are 3 problems fixed here:
>>  - The  `EnterInterpOnlyModeClosure::do_threads` is taking the `JvmtiThreadState` with the `jt->jvmti_thread_state()` which is incorrect when we have a deal with a carrier thread. The target state is known at the point when the `HandshakeClosure` is set, so the fix is to pass it as a constructor parameter.
>>  - The `state->is_pending_interp_only_mode())` was processed at mounts only but it has to be processed for unmounts as well. 
>>  - The test `test/hotspot/jtreg/serviceability/jvmti/vthread/MethodExitTest/libMethodExitTest.cpp` has a wrong assumption that there can't be `MethodExit` event on the carrier thread when the function `breakpoint_hit1` is being executed. However, it can happen if the virtual thread gets unmounted.
>>  
>>  The fix also includes new test case `vthread/CarrierThreadEventNotification` developed by Patricio.
>>  
>>  Testing:
>>  - Ran new test case locally
>>  - Ran mach5 tiers 1-6
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review: refactored def and use of process_pending_interp_only()

test/hotspot/jtreg/serviceability/jvmti/vthread/CarrierThreadEventNotification/libCarrierThreadEventNotification.cpp line 40:

> 38: 
> 39: static const char* CTHREAD_NAME_START = "ForkJoinPool";
> 40: static const size_t CTHREAD_NAME_START_LEN = (int)strlen("ForkJoinPool");

`(int)` cast is not needed

test/hotspot/jtreg/serviceability/jvmti/vthread/CarrierThreadEventNotification/libCarrierThreadEventNotification.cpp line 58:

> 56:       cthreads[ct_cnt++] = jni->NewGlobalRef(thread);
> 57:     }
> 58:     deallocate(jvmti, jni, (void*)tname);

cast to `void*` is not needed

test/hotspot/jtreg/serviceability/jvmti/vthread/CarrierThreadEventNotification/libCarrierThreadEventNotification.cpp line 96:

> 94:     }
> 95:     jvmtiError err = jvmti->Deallocate((unsigned char*)carrier_threads);
> 96:     check_jvmti_status(jni, err, "deallocate: error in JVMTI Deallocate call");

replace with `deallocate(jvmti, jni, carrier_threads);` ?

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PR Review Comment: https://git.openjdk.org/jdk/pull/19438#discussion_r1623060427
PR Review Comment: https://git.openjdk.org/jdk/pull/19438#discussion_r1623061692
PR Review Comment: https://git.openjdk.org/jdk/pull/19438#discussion_r1623061890