PING: Re: RFR (XS): 8244571: assert(!_thread->is_pending_jni_exception_check()) failed: Pending JNI Exception Check during class loading

[David Holmes]

Hi Serguei,

On 22/05/2020 4:17 pm, serguei.spitsyn at oracle.com wrote:
> PING: This is pretty small and easy to review fix.
> 
> Thanks!
> Serguei
> 
> 
> On 5/19/20 09:28, serguei.spitsyn at oracle.com wrote:
>> Please, review fix for:
>> https://bugs.openjdk.java.net/browse/JDK-8244571
>>
>> Webrev:
>> http://cr.openjdk.java.net/~sspitsyn/webrevs/2020/8244571-jvmti-test-jnicheck.1/
>>
>> Summary:
>>   There are two places in the native part of test that cause assert 
>> and WARNING with the -Xcheck:jni.
>>   The assert is because there is no check for pending exception after 
>> the call to:
>> jni->CallBooleanMethod(klass, is_hid_mid);
>>   Using a JNI ExceptionCheck()after the call fixes the issue.

   bool res = jni->CallBooleanMethod(klass, is_hid_mid);
   if (jni->ExceptionCheck()) {
     LOG0("is_hidden: Exception in jni CallBooleanMethod\n");
   }
   return res;

That will fix the pending_jni_exception_check error, but if an exception 
actually occurs what will be returned? And whatever is returned, the 
callers of this method don't themselves check for pending exceptions so 
they will treat it as if the exception didn't occur - at least until we 
finally return to Java code. Perhaps any exception should result in 
jni->FatalError as happens with any JVMTI error?

>>   The following call to the JVM TI function:
>> err = jvmti->GetClassLoaderClasses(loader, &count, &loader_classes);
>>   produces the warning (with a java level stack trace): WARNING: JNI 
>> local refs: 94, exceeds capacity: 32
>>   It is because the GetClassLoaderClasses returns an array of local 
>> references to the loader classes.
>>   Using a JNI EnsureLocalCapacity() before the JVM TI call also fixes 
>> the issue.

The warning suggests using 1024 is a bit of overkill. :)

Cheers,
David

>>
>> Testing:
>>   Running the test test/hotspot/jtreg/serviceability/jvmti/HiddenClass 
>> locally.
>>   Will run a mach5 job as well.
>>
>> Thanks,
>> Serguei
>>
>>
>>
>