RFR: JDK-8152690: main thread does not have native thread name

[Kumar Srinivasan]

On 4/19/2016 1:32 PM, David Holmes wrote:
> On 20/04/2016 3:00 AM, Kumar Srinivasan wrote:
>> Hi David,
>>
>>   493     /* Set native thread name. */
>>   494     SetNativeThreadName(env, "main");
>>   495
>>   496     /* Invoke main method. */
>>   497     (*env)->CallStaticVoidMethod(env, mainClass, mainID, 
>> mainArgs);
>>
>> Supposing an exception is thrown in 494 (a very remote case),
>> will we not re-enter the VM in 497 with an exception ?
>
> Yes as I said:
>
>> 1712     NULL_CHECK(nameString = (*env)->NewStringUTF(env, name));
>> 1713     (*env)->CallVoidMethod(env, currentThread, setNativeNameID,
>> 1714                            nameString, JNI_TRUE);
>>
>> As above NULL_CHECK is fine here, but we should check for and clear 
>> any pending exception after CallVoidMethod.
>
Agreed.

Kumar

> Thanks,
> David
>
>> Kumar
>>
>>> On 19/04/2016 10:54 PM, Gerard Ziemski wrote:
>>>>
>>>>> On Apr 19, 2016, at 12:04 AM, David Holmes <david.holmes at oracle.com>
>>>>> wrote:
>>>>>
>>>>> On 19/04/2016 9:28 AM, Yasumasa Suenaga wrote:
>>>>>> Hi Gerard,
>>>>>>
>>>>>> 2016/04/19 3:14 "Gerard Ziemski" <gerard.ziemski at oracle.com
>>>>>> <mailto:gerard.ziemski at oracle.com>>:
>>>>>>>
>>>>>>> hi Yasumasa,
>>>>>>>
>>>>>>> Nice work. I have 2 questions:
>>>>>>>
>>>>>>> ========
>>>>>>> File: java.c
>>>>>>>
>>>>>>> #1 Shouldn’t we be checking for “(*env)->ExceptionOccurred(env)”
>>>>>> after every single JNI call? In this example instead of NULL_CHECK,
>>>>>> should we be using CHECK_EXCEPTION_NULL_LEAVE macro?
>>>>>>
>>>>>> It is not critical if we encounter error at JNI function call  
>>>>>> because
>>>>>> we cannot set native thread name only.
>>>>>> So I think that we do not need to leave from launcher process.
>>>>>
>>>>> I agree we do not need to abort if an exception occurs (and in fact
>>>>> I don't think an exception is even possible from this code), but we
>>>>> should ensure any pending exception is cleared before any futher JNI
>>>>> calls might be made. Note that NULL_CHECK is already used
>>>>> extensively throughout the launcher code - so if this usage is wrong
>>>>> then it is all wrong! More on this code below ...
>>>>
>>>> Isn’t there a risk that:
>>>>
>>>> (*env)->CallVoidMethod(env, currentThread, setNativeNameID,
>>>> +                           nameString, JNI_TRUE);
>>>>
>>>> will raise an exception?
>>>>
>>>> In the least, shouldn’t we clear any possible pending exceptions at
>>>> the beginning of “SetNativeThreadName“, as you say, but also at the
>>>> very end?
>>>
>>> I was actually saying at the end, after the call (even though I don't
>>> think any exceptions are possible - except for "async" exceptions of
>>> course). We shouldn't be able to get to the call with any exception
>>> pending as in that case the JNI calls will be returning NULL and we
>>> will exit - again this pattern is used extensively in the launcher.
>>>
>>> David
>>>
>>>>
>>>> cheers
>>>>
>>