RFR (s): JDK-8011802 NPG: init_dependencies in class loader data graph can cause invalid CLD

[Mikael Gerdin]

Thanks Stefan and Coleen.

I'll go ahead and push this change.
Also, I forgot to mention that I tested this change with Nashorn's 
test262parallel.

/Mikael

On 2013-04-22 20:11, Coleen Phillimore wrote:
>
> I agree.  This does look good.
> Thanks,
> Coleen
>
> On 04/22/2013 02:07 PM, Stefan Karlsson wrote:
>> Looks good.
>>
>> StefanK
>>
>> On 2013-04-22 14:38, Mikael Gerdin wrote:
>>> Hi,
>>>
>>> here is my suggested fix for the ClassLoaderData initialization issue
>>> that David brought up in the review thread for JDK-8010196.
>>>
>>> The problem:
>>> Upon initialization of a ClassLoaderData (from
>>> ClassLoaderDataGraph::add) the newly created CLD is added to the
>>> ClassLoderData linked list and to the hidden field in the
>>> java/lang/ClassLoader object before we call init_dependencies to
>>> create the Java object array.
>>> Since the creation of the object array can throw a Java Exception
>>> (OOME) we need to be able to clean up if that happens.
>>>
>>>
>>> The fix:
>>> Instead of trying to undo what we did when adding the CLD I suggest
>>> that we first try to init_dependencies and if that succeeds we
>>> proceed to try to add the CLD to the ClassLoader and the list.
>>> If two threads are simultaneously trying to create a CLD for a loader
>>> we will now allocate a few unnecessary object arrays since we
>>> allocate them optimistically but since we don't hang on to them they
>>> should not cause any memory overhead.
>>>
>>> I also took the liberty to change the way we signal that a CLD is for
>>> an anonymous class to use a boolean instead of passing a null value
>>> to the CLD** and moved all the code to write the CLD* into the
>>> ClassLoader to ClassLoaderDataGraph::add. The code motion is
>>> necessary since init_dependencies may trigger a GC and the CLD**
>>> which was passed in was in fact a raw pointer into the ClassLoader in
>>> the Java heap.
>>>
>>> Unfortunately I can't use CHECK_NULL when calling init_dependencies
>>> since I need to delete the cld before returning.
>>>
>>> Webrev: http://cr.openjdk.java.net/~mgerdin/8011802/webrev.0/
>>>
>>> bugs.sun.com: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8011802
>>> jbs: https://jbs.oracle.com/bugs/browse/JDK-8011802
>>>
>>> /Mikael
>>
>