On Sat, 18 Feb 2023 01:30:27 GMT, Serguei Spitsyn <sspit...@openjdk.org> wrote:
>> src/hotspot/share/prims/jvmtiEnv.cpp line 952:
>>
>>> 950: }
>>> 951: // protect thread_oop as a safepoint can be reached in disabler
>>> destructor
>>> 952: self_tobj = Handle(current, thread_oop);
>>
>> If you move this after line 953 then you can delete line 932 and just have:
>>
>> Handle self_tobj = Handle(current, thread_oop);
>
> Thank you for looking at this PR, David!
> Please, note a disabler at L938. A safepont can be reached in its destructor.
> Also, see the comment at L952:
>
> 937 {
> 938 JvmtiVTMSTransitionDisabler disabler(true);
> 939 ThreadsListHandle tlh(current);
> 940
> 941 err = get_threadOop_and_JavaThread(tlh.list(), thread, &java_thread,
> &thread_oop);
> 942 if (err != JVMTI_ERROR_NONE) {
> 943 return err;
> 944 }
> 945
> 946 // Do not use JvmtiVTMSTransitionDisabler in context of self suspend
> to avoid deadlocks.
> 947 if (java_thread != current) {
> 948 err = suspend_thread(thread_oop, java_thread, /* single_suspend */
> true, nullptr);
> 949 return err;
> 950 }
> 951 // protect thread_oop as a safepoint can be reached in disabler
> destructor
> 952 self_tobj = Handle(current, thread_oop);
> 953 }
> it means there are now many places that can block for safepoints that
> previously wouldn't and it is very to hard to tell if that is okay or not.
We partially rely on testing and good test coverage here.
-------------
PR: https://git.openjdk.org/jdk/pull/12550
