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

[Ioi Lam]

Coleen, Serguei & Max,

Thanks for the reviews. I will push.

- Ioi

On 1/5/17 10:27 AM, Max Ockner wrote:
> 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
>>>>
>>>
>>
>