On Mon, 25 Jan 2021 15:01:25 GMT, Anton Kozlov <[email protected]> wrote:
>> src/hotspot/share/jfr/instrumentation/jfrJvmtiAgent.cpp line 87:
>>
>>> 85: JavaThread* jt = JavaThread::thread_from_jni_environment(jni_env);
>>> 86: DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_native(jt));;
>>> 87: Thread::WXWriteFromExecSetter wx_write;
>>
>> Is this on every transition to VM from Native? Would it be better to add to
>> ThreadInVMfromNative like the ResetNoHandleMark is?
>
> I've tried to do something like this initially. The idea was to use Write in
> VM state and Exec in Java and Native states. However, for example, JIT runs
> in the Native state and needs Write access. So instead, W^X is managed on
> entry and exit from VM code, in macros like JRT_ENTRY. Unfortunately, not
> every JVM entry function is defined with an appropriate macro (at least for
> now), so I had to add explicit W^X state management along with the explicit
> java thread state, like here.
Yes, that's why I thought it should be added to the classes
ThreadInVMfromNative, etc like:
class ThreadInVMfromNative : public ThreadStateTransition {
ResetNoHandleMark __rnhm;
We can look at it with cleaning up the thread transitions RFE or as a
follow-on. If every line of ThreadInVMfromNative has to have one of these
Thread::WXWriteVerifier __wx_write; people are going to miss them when
adding the former.
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PR: https://git.openjdk.java.net/jdk/pull/2200
