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

[David Holmes]

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.

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
>>>
>