RFR: 8038332: The trace event vm/class/load is not always being sent

[Max Ockner]

David,

New webrev: 
http://cr.openjdk.java.net/~mockner/8038332.02/src/share/vm/classfile/systemDictionary.cpp.cdiff.html
I have added the check you suggested before triggering the event:

if (HAS_PENDING_EXCEPTION || k.is_null()) {
     return NULL;
}

Thanks,
Max

On 6/13/2016 6:40 PM, David Holmes wrote:
> Hi Max,
>
> On 14/06/2016 3:42 AM, Max Ockner wrote:
>> Jiangli,
>> Thanks for looking.  I didn't see anything that looked like it might
>> produce duplicate events. However, I did see some additional places
>> where it looks like no event is fire.
>>
>> Can anyone point me to the event specs?
>
> I'm not sure there is any spec for this. Even JFR doesn't seem to 
> document individual events and when they are triggered.
>
> Your change does not look right however as you are posting the 
> classload event regardless of the exception state. If you look at 
> SystemDictionary::resolve_instance_class_or_null, it only posts after 
> checking the load was successful:
>
>  892   if (HAS_PENDING_EXCEPTION || k.is_null()) {
>  893     return NULL;
>  894   }
>  895
>  896   post_class_load_event(class_load_start_time, k, class_loader);
>
> Similarly, SystemDictionary::parse_stream, has various CHECK macros 
> that will cause a return on exception, prior to getting to the point 
> of posting the load event. So you also need to add a check for a 
> pending exception and that k is not null, I think, before posting the 
> event.
>
I have added this check.
> BTW I would have expected to see trace-events generated at 
> approximately the same locations as the corresponding JVMTI events. 
> That does not seem to be the case which seems very strange to me. The 
> notion of "loading a class" seems to be spread across far too many 
> functions to me.
>
> Thanks,
> David
>
>> Thanks,
>> Max
>>
>> On 6/9/2016 4:39 PM, Jiangli Zhou wrote:
>>> Hi Max,
>>>
>>> Looks ok. The only possible issue is more than one event might be sent
>>> in some of the call paths. But my quick search didn’t find any of such
>>> case.
>>>
>>> Thanks,
>>> Jiangli
>>>
>>>> On Jun 9, 2016, at 11:05 AM, Max Ockner <max.ockner at oracle.com> wrote:
>>>>
>>>> Hello,
>>>>
>>>> Please review this small fix which causes the vm/class/load event to
>>>> be fired from JVM_DefineClass() and JVM_DefineClassWithSource().
>>>>
>>>> Webrev: http://cr.openjdk.java.net/~mockner/8038332/
>>>> Bug: https://bugs.openjdk.java.net/browse/JDK-8038332
>>>>
>>>> The vm/class/load event  (EventClassLoad) was previously fired in 2
>>>> places:
>>>>
>>>> SystemDictionary::parse_stream
>>>> SystemDictionary::resolve_instance_class_or_null
>>>>
>>>> parse_stream is the standard option for creating a klass from a
>>>> stream, but JVM_DefineClass uses a different function:
>>>>
>>>> SystemDictionary::resolve_from_stream.
>>>>
>>>> This did not fire a vm/class/load event. Now it does fire the event.
>>>>
>>>> Sanity tested with jtreg runtime. Issue was reproduced and tested
>>>> using the reproducer script attached to the bug
>>>>
>>>> Thanks,
>>>> Max
>>