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

[Coleen Phillimore]

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
>