RFR: 8027429: Add diagnostic command VM.info to get hs_err print-out

[David Holmes]

On 29/10/2015 10:02 PM, Coleen Phillimore wrote:
>
>
> On 10/29/15 7:58 AM, David Holmes wrote:
>> On 29/10/2015 9:26 PM, Coleen Phillimore wrote:
>>>
>>> So I actually disagree.  I don't think there should be an additional
>>> separate mechanism to get the same information that we get with hs_err
>>> reporting.  I've wanted to have a feature like this for a long time.
>>>
>>> I pre-reviewed this change and I thought it looked good in general. I
>>> didn't see the thread iteration problem that Fred refers to below, but I
>>> think the individual problems can be fixed.
>>>
>>> The last thing I want is this code to be copied somewhere else.
>>
>> Factored as needed not copied. VMError is not an "info" reporting
>> mechanism.
>
> If you look at the things that are reported in each "STEP", there's a
> small amount of code and the order is important.

The order is less important in an "info" request I would think.

> I'd like the vm info to use the same order and report what it can do
> safely.   Refactoring 5 lines of code into functions doesn't make sense.

I need to consider exactly what it is the "info" needs to report in more 
detail. There are existing facilities (system properties, management 
APIs) for various bits of runtime information, which VMError can't 
utilize but a Dcmd can.

David

> Coleen
>
>>
>> David
>>
>>> Coleen
>>>
>>> On 10/28/15 8:48 PM, David Holmes wrote:
>>>> I agree with Fred, this kind of info reporting should not be
>>>> piggy-backed onto VMError handling for the reasons stated (and the
>>>> error handling logic is complicated enough as it is!). For things like
>>>> thread lists there are already safe management functions that
>>>> can/should be used.
>>>>
>>>> Thanks,
>>>> David H.
>>>>
>>>> On 29/10/2015 3:29 AM, Frederic Parain wrote:
>>>>> Hi David,
>>>>>
>>>>> I haven't review all the code yet, but I'm concerned with the
>>>>> fact that the diagnostic command is calling VMError::report().
>>>>> This method has been implemented to be executed in the particular
>>>>> context of fatal errors, and its usage while the VM is running
>>>>> normally seems dangerous.
>>>>>
>>>>> For instance, VMError::report() consciously avoids grabbing locks
>>>>> because of the risk of deadlock during the error reporting.
>>>>> The consequence is that some data structures are browsed in
>>>>> an unsafe way. One example: VMError::report() calls
>>>>> Threads::print_on_error() which iterates over the thread
>>>>> list *without owning the Threads_lock*.
>>>>>
>>>>> The implementation of the diagnostic command seems also to
>>>>> exclude a lot of reporting from the initial VMError::report()
>>>>> method. Have you considered implementing a new MT-safe reporting
>>>>> method rather than trying to modify the special VMError::report()
>>>>> methods? (Note that some code factorization between VMError::report()
>>>>> and this new method should be possible).
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Fred
>>>>>
>>>>> On 28/10/2015 17:18, david buck wrote:
>>>>>> Hi!
>>>>>>
>>>>>> Please review my change for this small enhancement.
>>>>>>
>>>>>> bug: https://bugs.openjdk.java.net/browse/JDK-8027429
>>>>>> webrev: http://cr.openjdk.java.net/~dbuck/8027429_jdk9_01/
>>>>>>
>>>>>> Cheers,
>>>>>> -Buck
>>>>>
>>>
>