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

[Serguei Spitsyn]

On Thu, 30 May 2024 01:03:01 GMT, Alex Menkov <amenkov 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
>
> test/hotspot/jtreg/serviceability/jvmti/vthread/CarrierThreadEventNotification/libCarrierThreadEventNotification.cpp line 44:
> 
>> 42: static jint
>> 43: get_cthreads(JNIEnv* jni, jthread** cthreads_p) {
>> 44:   jthread* tested_cthreads = NULL;
> 
> This local variable has the same name as global.
> I'd suggest to rename the local var or remove it (and the function should set both `tested_cthreads` and ` cthread_cnt`)

Thanks. Renamed the local to `cthreads` and the global to `carrier_threads`.

> test/hotspot/jtreg/serviceability/jvmti/vthread/CarrierThreadEventNotification/libCarrierThreadEventNotification.cpp line 91:
> 
>> 89:     for (int i = 0; i < cthread_cnt; i++) {
>> 90:       jthread thread = tested_cthreads[i];
>> 91:       char* tname = get_thread_name(jvmti, jni, thread);
> 
> `tname` is not needed

Removed, thanks.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/19438#discussion_r1619726804
PR Review Comment: https://git.openjdk.org/jdk/pull/19438#discussion_r1619728368