PING: RFR: JDK-8145788: JVM crashes with -XX:+EnableTracing

Yasumasa Suenaga yasuenag at gmail.com
Mon Jan 11 10:08:39 UTC 2016 

Hi Markus, David,

I agree the solution of Markus too!


Thanks,

Yasumasa


On 2016/01/11 18:48, Markus Gronlund wrote:
> Hi David,
>
> Thanks for pointing to the locked branch as well.
>
> Thanks to the bootstrap aware logic in defaultStream::hold(intx writer_id) this should be ok as is:
>
> ttyLocker will call the hold() member function which defaults to single threaded behavior during bootstrap (DefaultStream::NOWRITER). This is accomplished by checking the availability of both ttyLock as well as Thread::current_or_null().
>
> Cheers
> Markus
>
> -----Original Message-----
> From: David Holmes
> Sent: den 11 januari 2016 02:39
> To: Markus Gronlund; Yasumasa Suenaga
> Cc: serviceability-dev at openjdk.java.net
> Subject: Re: PING: RFR: JDK-8145788: JVM crashes with -XX:+EnableTracing
>
> Hi Markus,
>
> Thanks very much for stepping in on this one. I like your solution to this particular problem.
>
> Aside: I noticed in writeEvent there is also UseLockedTracing and I'm wondering if that will also lead to an assertion failure due to no current thread?
>
> Thanks,
> David
>
> On 11/01/2016 9:25 AM, Markus Gronlund wrote:
>> Hi Yasumasa,
>>
>> Apologies for the delay in getting a response to you.
>>
>> Thanks for reporting and attempting to fix this issue.
>>
>> I have investigated this a bit as well as trying out your suggested patch.
>>
>> I must admit it is hard to get this right at this early stage of the VM, and though I appreciated your effort for resolution, the patch suggestion will not work out of the box unfortunately.
>>
>> I have summarized some of my findings and reasoning here:
>>
>> http://cr.openjdk.java.net/~mgronlun/8145788/notes.txt
>>
>> As you can see, Thread::current() cannot be called at this stage. If we update to instead call Thread::current_or_null(), you will now run into problems in the interplay between an explicit delete of a Cheap allocated ResourceArea and the subsequent ResourceMark destructor. Here, the rm destructor asserts since it expects _nesting_level > 0, but that data has already been invalidated.
>>
>> You could accomplish all of this by doing:
>>
>> +    bool thread_has_resource = Thread::current_or_null() != NULL;
>> +    ResourceArea *area = thread_has_resource
>> +                           ? Thread::current()->resource_area()
>> +                           : new (mtTracing)ResourceArea(Chunk::non_pool_size);
>> +    {
>> +      ResourceMark rm(area);
>> +      if (UseLockedTracing) {
>> +        ttyLocker lock;
>> +        writeEventContent();
>> +      } else {
>> +        writeEventContent();
>> +      }
>> +    }
>> +
>> +    if (!thread_has_resource) {
>> +      delete area;
>>        }
>>
>>
>> However, it is getting a bit complex. In addition, now every trace statement needs to check Thread::current_or_null()..
>>
>> If you look at my reasoning in the second part, I think we can fix this in an easier way.
>>
>> You can find my suggestion as a webrev here:
>>
>> http://cr.openjdk.java.net/~mgronlun/8145788/
>>
>> Please try the patch out to see if you are ok with it.
>>
>> Thanks for your patience
>>
>> Best regards
>> Markus
>>
>>
>>
>> -----Original Message-----
>> From: Yasumasa Suenaga [mailto:yasuenag at gmail.com]
>> Sent: den 10 januari 2016 14:03
>> To: serviceability-dev at openjdk.java.net
>> Subject: PING: RFR: JDK-8145788: JVM crashes with -XX:+EnableTracing
>>
>> Ping: What do you think about this issue?
>>
>> On 2016/01/06 15:36, David Holmes wrote:
>>> Pinging the serviceability tracing experts please!
>>>
>>> David
>>>
>>> On 24/12/2015 12:25 AM, Yasumasa Suenaga wrote:
>>>> Hi David,
>>>>
>>>>>>         1. Initialize JavaThread before calling apply_ergo() in create_vm().
>>>>>
>>>>> That is not likely to be an option - it would likely be far too
>>>>> disruptive to the initialization sequence.
>>>>
>>>> Agree. Thus I choose 2.
>>>>
>>>>> We will have to wait for the tracing experts to have a good look at
>>>>> this.
>>>>
>>>> I'm waiting that the tracing experts join this discussion.
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>> On 2015/12/23 13:20, David Holmes wrote:
>>>>> Hi Yasumasa,
>>>>>
>>>>> On 23/12/2015 11:49 AM, Yasumasa Suenaga wrote:
>>>>>> Hi David,
>>>>>>
>>>>>> I've added callstack when JVM crashed:
>>>>>>
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8145788?focusedCommentId=
>>>>>> 1
>>>>>> 3880225&page=com.atlassian.jira.plugin.system.issuetabpanels:comme
>>>>>> n
>>>>>> t-tabpanel#comment-13880225
>>>>>
>>>>> Thanks for that.
>>>>>
>>>>>> This crash occurrs in Arguments::apply_ergo() in Threads::create_vm().
>>>>>> apply_ergo() calls before JavaThread initialization.
>>>>>>
>>>>>> I think that TraceEvent can avoid crash with two approach:
>>>>>>
>>>>>>         1. Initialize JavaThread before calling apply_ergo() in create_vm().
>>>>>
>>>>> That is not likely to be an option - it would likely be far too
>>>>> disruptive to the initialization sequence.
>>>>>
>>>>>>         2. Avoid crash at TraceEvent when it is called before JavaThread initialization.
>>>>>
>>>>> Or don't call it at all.
>>>>>
>>>>> We will have to wait for the tracing experts to have a good look at
>>>>> this. We end up in code that is not expecting to be run before more
>>>>> of the VM is initialized, so we have to look at what else may be
>>>>> being assumed and then decide whether to handle the situation or avoid it.
>>>>>
>>>>> Thanks,
>>>>> David
>>>>>
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Yasumasa
>>>>>>
>>>>>>
>>>>>> On 2015/12/22 21:19, David Holmes wrote:
>>>>>>> On 19/12/2015 1:50 AM, Yasumasa Suenaga wrote:
>>>>>>>> Hi all,
>>>>>>>>
>>>>>>>> I encountered JVM crash when I passed -XX:+EnableTracing.
>>>>>>>>
>>>>>>>>          I checked core image, it crashed in EventBooleanFlagChanged::writeEvent()
>>>>>>>>          which is called by Arguments::apply_ergo() because thread had not been
>>>>>>>>          initialized. (JVM seems to log changing GC algorithm to
>>>>>>>> G1.)
>>>>>>>
>>>>>>> This seems like a logic error to me - something is trying to
>>>>>>> happen too early during VM initialization. We need to look at
>>>>>>> exactly what we are trying to do here, not just work around the crash.
>>>>>>>
>>>>>>> David
>>>>>>> -----
>>>>>>>
>>>>>>>>          writeEvent() uses ResourceMark. Default constructor of ResourceMark uses
>>>>>>>>          ResourceArea in current thread. So ResourceMark in writeEvent() should
>>>>>>>>          pass valid ResourceArea.
>>>>>>>>
>>>>>>>> I think this issue is in traceEventClasses.xsl .
>>>>>>>> However, my environment (GCC 5.3.1 on Fedora23) cannot build it
>>>>>>>> because -Werror=maybe-uninitialized was occurred.
>>>>>>>> So I also fixed them together.
>>>>>>>>
>>>>>>>> I've uploaded webrev. Could you review it?
>>>>>>>>
>>>>>>>> http://cr.openjdk.java.net/~ysuenaga/JDK-8145788/webrev.00/
>>>>>>>>
>>>>>>>> I'm jdk9 committer, however I cannot access JPRT.
>>>>>>>> So I need a sponsor.
>>>>>>>>
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Yasumasa
>>>>>>>>

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