RFR: 8085903: New fix for memory leak in ProtectionDomain cache

[Xuelei Fan]

I think hashMap.put() may be similar or more effective than
hashMap.putIfAbsent().  Is there a case that the key/weakPd is the same,
but the value/pc is different?

Xuelei

On 1/12/2016 11:01 PM, Sean Mullan wrote:
> Hi Ivan,
> 
> On 01/12/2016 09:38 AM, Ivan Gerasimov wrote:
>> Hi Sean!
>>
>> On 12.01.2016 16:26, Sean Mullan wrote:
>>> I received a private comment that there may be cases where the map's
>>> value is reclaimed by the garbage collector, but the key still exists.
>>> If that ProtectionDomain is subsequently used for permission checks, a
>>> Map.putIfAbsent method will not replace the value.
>>>
>>> So, I have added an additional check for this case in the PDCache.put
>>> method, and it instead uses the Map.replace method. Updated webrev:
>>>
>>
>> Wouldn't it be a little bit more efficient to use merge() here?
>>
>> Something like:
>> pdMap.merge(weakPd, v, (pv, nv) -> pv.get() != null ? pv : nv);
> 
> Yes - good catch!
> 
> Will update and send out new webrev after a round of testing ...
> 
> Thanks,
> Sean
> 
>>
>> Sincerely yours,
>> Ivan
>>
>>> http://cr.openjdk.java.net/~mullan/webrevs/8085903/webrev.01/
>>>
>>> --Sean
>>>
>>> On 01/08/2016 03:06 PM, Sean Mullan wrote:
>>>> Please review this fix for a memory leak in the ProtectionDomain cache
>>>> (which maps each ProtectionDomain to their granted
>>>> PermissionCollection). The memory leak only occurs if custom
>>>> permissions
>>>> are used in a policy file.
>>>>
>>>> http://cr.openjdk.java.net/~mullan/webrevs/8085903/webrev.00/
>>>>
>>>> Custom permissions cause a chain of strong references that link back to
>>>> the ProtectionDomain key used in the map, preventing it from being
>>>> removed (and also preventing the custom permission's URLClassLoader
>>>> from
>>>> being garbage collected). This fix wraps the PermissionCollection in a
>>>> SoftReference which allows the objects to be garbage collected in
>>>> response to memory demand.
>>>>
>>>> Thanks,
>>>> Sean
>>>
>>