Review Request JDK-8164512: Replace ClassLoader use of finalizer with phantom reference to unload native library

[mandy chung]

On 10/9/17 3:47 AM, Peter Levart wrote:
>
>
> On 10/09/2017 10:20 AM, Alan Bateman wrote:
>> On 06/10/2017 20:37, mandy chung wrote:
>>> :
>>>
>>> The native libraries map is now created lazily with 
>>> synchronization.    I keep the lazy initialization that will save to 
>>> create a CHM as many custom class loaders don't have native code.  I 
>>> think it's a good saving.   In addition, if we iniitialize the 
>>> static systemNativeLibraries at <clinit> time, it may want to avoid 
>>> using CHM as it changes the class initialization order.
>>>
>> Alternatively change nativeLibraries and systemNativeLibraries to 
>> volatile so the synchronization is only needed to initialize them. 
>> Otherwise this version (webrev.03) looks good to me.
>>
>> -Alan
>
> Yes Mandy, you could use volatile fields + double checked locking for 
> initialization.


Since this might affect JNI binding, I have avoided changing it to 
volatile in this patch until we get some performance number (I might be 
overly conversative).  I prefer to follow up this together in the lock 
cleanup RFE that David suggests.

> In addition, the initializers to 'null' value are not needed / are a 
> waste of instructions (the default is guaranteed by JLS):
>
> 2695     // Native libraries belonging to system classes.
> 2696     private static Map<String, NativeLibrary> 
> systemNativeLibraries = null;
> 2697
> 2698     // Native libraries associated with the class loader.
> 2699     private Map<String, NativeLibrary> nativeLibraries = null;

sure.
Mandy