RFR: 8292657: Calling GetLocalXXX from virtual thread with thread parameter set to NULL returns carrier locals

[Serguei Spitsyn]

On Fri, 26 Aug 2022 20:42:01 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> If JVM TI GetLocalXXX/SetLocalXXX is called from a virtual thread with the thread parameter set to NULL (meaning current thread) then it should get/set the value of the locals in the virtual thread frames. Instead, it reads the carrier thread locals and/or crashes.
>> 
>> The fix is that the relevant checking of the jthread parameter for NULL and adjusting it to current thread is added.
>> It is done in new utility `function current_thread_obj_or_resolve_external_guard(jthread thread)`. For more convenient testing the same adjustment is done in the JVM TI extension function `GetCarrierThread()`.
>> 
>> The test serviceability/jvmti/vthread/GetSetLocalTest is updated to add previously missed test coverage.
>> 
>> The test serviceability/jvmti/vthread/VThreadTest has been updated to adopt to update behavior of the `GetCarrierThread`.
>> 
>> The fix was verified with the test/hotspot/jtreg/serviceability/jvmti/vthread/ tests.
>> 
>> The fix was also tested with the existing JVM TI and JDI tests to make sure no regressions are introduced.
>
> test/hotspot/jtreg/serviceability/jvmti/vthread/GetSetLocalTest/libGetSetLocalTest.cpp line 316:
> 
>> 314:   Values values1 = { NULL, NULL, 2, 3L, (jfloat)4.2F, (jdouble)5.500000047683716 };
>> 315:   // jthread cthread = at_event ? get_carrier_thread(jvmti, jni, get_current_thread(jvmti, jni))
>> 316:   //                            : get_carrier_thread(jvmti, jni, vthread);
> 
> Is there a reason to keep this around?

You are right. Will remove this.

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PR: https://git.openjdk.org/jdk/pull/10051