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

[Ivan Gerasimov]

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);

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
>