RFR (xs): 8170959 unloading archived shared class caused crash

[Max Ockner]

Ioi,
This looks good to me.
Max

On 1/4/2017 8:37 PM, Coleen Phillimore wrote:
>
> Yes, I think this looks a lot better.
> Thanks!
> Coleen
>
> On 1/4/17 8:09 PM, Ioi Lam wrote:
>> Hi Coleen,
>>
>> Thanks for the suggestion. I've removed the assert. I needed to add a 
>> check for the _cached_class_file because for shared classes this 
>> field is not allocated from the C heap, but rather points into the 
>> shared archive.
>>
>> http://cr.openjdk.java.net/~iklam/jdk9/8170959-archived-shared-class-unloading.v02/ 
>>
>>
>> Thanks
>> - Ioi
>>
>> On 1/4/17 3:54 PM, Coleen Phillimore wrote:
>>>
>>> Hi Ioi,
>>>
>>> It seems like there would be leaks if you don't release some of 
>>> these C_heap structures.  Should the assert just be removed?
>>> Except the constant pool release_C_heap_structures unreferences 
>>> symbols, and that shouldn't be done if the constant pool is shared.
>>> thanks,
>>> Coleen
>>>
>>> On 1/4/17 6:33 PM, Ioi Lam wrote:
>>>> Hi,
>>>>
>>>> Please review this small fix:
>>>>
>>>> https://bugs.openjdk.java.net/browse/JDK-8170959
>>>> http://cr.openjdk.java.net/~iklam/jdk9/8170959-archived-shared-class-unloading.v01/ 
>>>>
>>>>
>>>> Please note that this is a closed bug and it's related to unloading
>>>> shared classes loaded by custom class loaders. The test case is
>>>> in the closed repo.
>>>>
>>>> The bug happened with the following call stack
>>>>
>>>>         "assert(!this->is_shared()) failed"
>>>>     in InstanceKlass::release_C_heap_structures ()
>>>>     in InstanceKlass::release_C_heap_structures ()
>>>>     in ClassLoaderData::classes_do 
>>>> (f=<InstanceKlass::release_C_heap_structures(InstanceKlass*)>)
>>>>     in ClassLoaderData::~ClassLoaderData ()
>>>>     in ClassLoaderDataGraph::purge ()
>>>>     in G1CollectedHeap::do_full_collection ()
>>>>
>>>> The fix is to avoid doing the clean up if the unloaded class is 
>>>> shared.
>>>> Proper clean up is deferred to JDK 10 (bug JDK-8140287).
>>>>
>>>> Thanks
>>>> - Ioi
>>>
>>
>