RFR: 8260589: Crash in JfrTraceIdLoadBarrier::load(_jclass*)

[Denghui Dong]

On Sun, 31 Jan 2021 13:30:43 GMT, Denghui Dong <ddong at openjdk.org> wrote:

>> hi,
>> 
>> Could I have a review of this fix?
>> 
>> If we run the following code snippet, will get a crash
>> class JFRDemo {
>>     public static void main(String[] args) {
>>         Recording r = new Recording();
>>         r.enable("MyEvent");
>>         r.start();
>> 
>>         MyEvent event = new MyEvent();
>>         event.begin();
>>         event.clazz = long.class;
>>         event.commit();
>>     }
>> }
>> 
>> class MyEvent extends Event {
>> 
>>     @Label("Class")
>>     public Class clazz;
>> }
>
> Add some information to facilitate this issue to be reviewed more easily.
> 
> We will get a crash if we run the above code,, and the stack trace is as follows:
> 
> Stack: [0x00007fa12b2f3000,0x00007fa12b3f4000],  sp=0x00007fa12b3f2790,  free space=1021k
> Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
> V  [libjvm.so+0x89d649]  JfrTraceIdLoadBarrier::load(_jclass*)+0x39
> V  [libjvm.so+0x86090e]  jfr_class_id+0x7e
> j  jdk.jfr.internal.JVM.getClassIdNonIntrinsic(Ljava/lang/Class;)J+0 jdk.jfr
> j  jdk.jfr.internal.EventWriter.putClass(Ljava/lang/Class;)V+14 jdk.jfr
> j  jdk.jfr.internal.handlers.EventHandler1699_1612098965420-78137.write(JJLjava/lang/Class;)V+35 jdk.jfr
> j  MyEvent.commit()V+73
> j  JFRCrashTest.main([Ljava/lang/String;)V+39
> v  ~StubRoutines::call_stub
> V  [libjvm.so+0x82aef5]  JavaCalls::call_helper(JavaValue*, methodHandle const&, JavaCallArguments*, Thread*)+0x2d5
> V  [libjvm.so+0x8be315]  jni_invoke_static(JNIEnv_*, JavaValue*, _jobject*, JNICallType, _jmethodID*, JNI_ArgumentPusher*, Thread*) [clone .isra.0] [clone .constprop.1]+0x345
> V  [libjvm.so+0x8c0b3f]  jni_CallStaticVoidMethod+0x12f
> C  [libjli.so+0x4647]  JavaMain+0xd27
> C  [libjli.so+0x8079]  ThreadJavaMain+0x9
> 
> Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
> j  jdk.jfr.internal.JVM.getClassIdNonIntrinsic(Ljava/lang/Class;)J+0 jdk.jfr
> j  jdk.jfr.internal.EventWriter.putClass(Ljava/lang/Class;)V+14 jdk.jfr
> j  jdk.jfr.internal.handlers.EventHandler1699_1612098965420-78137.write(JJLjava/lang/Class;)V+35 jdk.jfr
> j  MyEvent.commit()V+73
> j  JFRCrashTest.main([Ljava/lang/String;)V+39
> v  ~StubRoutines::call_stub
> 
> The root cause is that basic types, including void, do not have corresponding Klass objects inside the virtual machine, so call java_lang_Class::as_Klass will return NULL and crash in JfrTraceIdLoadBarrier::load finally.
> 
> My solution is adding two serializers, one for the names of basic types, and one for basic types.
> 
> I am not sure about the setting of the class loader is right or not, I currently set it to 0 directly.

JVM.getClassId() doesn't seem to be used, so I didn't modify the implementation of the corresponding intrinsics.

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PR: https://git.openjdk.java.net/jdk/pull/2295