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

[Jiangli Zhou]

+1

Thanks,
Jiangli

> On Jun 23, 2016, at 12:32 PM, Coleen Phillimore <coleen.phillimore at oracle.com> wrote:
> 
> 
> This looks so much better.
> Thanks!
> Coleen
> 
> On 6/23/16 2:28 PM, Max Ockner wrote:
>> Hello again!
>> 
>> New webrev: http://cr.openjdk.java.net/~mockner/8038332.03/
>> 
>> Thanks,
>> Max
>> 
>> 
>> On 6/22/2016 10:53 PM, Coleen Phillimore wrote:
>>> 
>>> 
>>> On 6/22/16 5:02 PM, Ioi Lam wrote:
>>>> Instead of using Exceptions::_throw_msg directly, I think it's better to use the macro
>>>> 
>>>>    THROW_MSG_NULL(vmSymbols::java_lang_SecurityException(), message);
>>>> 
>>>> It will do the "return NULL" for you, so there's no danger of forgetting doing it.
>>> 
>> Done.
>> 
>>> Agree.
>>> Coleen
>>>> 
>>>> Thanks
>>>> - Ioi
>>>> 
>>>> On 6/22/16 12:13 PM, Coleen Phillimore wrote:
>>>>> 
>>>>> Hi,
>>>>> 
>>>>> Can I suggest actually fixing this code?  Please?
>>>>> 
>>>>> Instead of returning THREAD in all the calls in parse_stream(), they should have CHECK_NULL.   Then all the if (!HAS_PENDING_EXCEPTION) conditionals can be removed and the logic fixed.
>>>>> 
>>>>> The only reason to have THREAD as the last parameter is if there's cleanup that needs to be done in the case of an exception, which is rare and I verified not the case in this function.
>>>>> 
>>>>> After this code put a return NULL;
>>>>> 
>>>>>    Exceptions::_throw_msg(THREAD_AND_LOCATION,
>>>>>      vmSymbols::java_lang_SecurityException(), message);
>>>>> //  add return NULL;
>>>>>  }
>>>>> 
>>>>> Otherwise, the code to add the event looks good.
>>>>> 
>>>>> Thanks,
>>>>> Coleen
>>>>> 
>>>>> 
>>>>> On 6/22/16 1:53 PM, Jiangli Zhou wrote:
>>>>>> Hi Max,
>>>>>> 
>>>>>> I see there is already an ‘if (!HAS_PENDING_EXCEPTION)’ check at line 1170 before the debug_only code. Maybe you cloud place the post_class_load_event() in there so it only post the event when there is no pending exception. That way you don’t need to change the existing logic and add the additional checks.
>>>>>> 
>>>>>> Thanks,
>>>>>> Jiangli
>>>>>> 
>>>>>>> On Jun 20, 2016, at 12:08 PM, Max Ockner <max.ockner at oracle.com> wrote:
>>>>>>> 
>>>>>>> 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
>>>>> 
>>>> 
>>> 
>> 
>