RFR: 8284855: Update needed to Cleaners added to jdk.crypto.cryptoki [v2]

[Brent Christian]

On Thu, 14 Apr 2022 22:01:18 GMT, Xue-Lei Andrew Fan <xuelei at openjdk.org> wrote:

>> src/jdk.crypto.cryptoki/share/classes/sun/security/pkcs11/wrapper/PKCS11.java line 168:
>> 
>>> 166:         // Calls disconnect() to cleanup the native part of the wrapper.
>>> 167:         Cleaner.create().register(this,
>>> 168:             () -> PKCS11.disconnect(pNativeData));
>> 
>> If I'm not mistaken each new call to Cleaner.create() will create a new cleaner and a new deamon thread for it, so it's not recommended to create one cleaner per object.
>> Also it might be worth double checking that the lambda created here doesn't capture `this`: IIRC there were some subtle cases where a lambda could unexpectedly capture `this`.
>> 
>> Also probably the cleaner itself can't be GC'ed while its thread is running but you might be relying on undocumented behavior. It would be more prudent to stick it in a static variable to retain a strong reference.
>
> Good points.  I may change to use a static method instead in the next commit.

The new Cleaner code for PasswordCallbackHandler in P11KeyStore.java also creates a new Cleaner instance per object.

Possible capture of 'this' is one reason I find `Runnable`s written out as static classes easier reason about than lambdas.

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PR: https://git.openjdk.java.net/jdk/pull/8248