Hi Kim, Roger,
I have prepared another webrev which addresses your outstanding concerns:
http://cr.openjdk.java.net/~plevart/jdk9-dev/removeInternalCleaner/webrev.04/
I added new method to Cleaner:
public boolean helpClean() { ... }
I think this form of method that just does one quantum of work and
returns a boolean indicating whether there's more work waiting is a
better fit for some clients that might want to do just a limited amount
of work at once (like for example sun.java2d.Disposer.pollRemove that
you mentioned). This method also deals with helping the ReferenceHandler
thread, which is necessary to be able to "squeeze" out all outstanding
work. As Cleaner is in the same package as Reference and helping
ReferenceHandler thread is implicitly included in Cleaner.helpClean(),
the JavaLangRefAccess interface and a field in SharedSecrets can be removed.
I also simplified the API in sun.nio.fs.NativeBuffer and replaced the
accessor of Cleanable with a simple void free() method (called free
because it deallocates memory).
I think this will have to be submitted to CCC for approval, right? Can
you help me with it?
Regards, Peter
On 02/17/2016 11:34 PM, Kim Barrett wrote:
On Feb 17, 2016, at 4:06 AM, Peter Levart <peter.lev...@gmail.com> wrote:
Hi Kim,
Thanks for looking into this. Answers inline…
Peter,
Thanks for the explanations.
On 02/17/2016 01:20 AM, Kim Barrett wrote:
However, I recall Roger saying there were existing tests that
failed when certain uses of sun.misc.Cleaner were replaced with
java.lang.ref.Cleaner. I don't remember the details, but maybe Roger
does.
If the failing test was the following:
java/nio/Buffer/DirectBufferAllocTest.java
...then it has been taken care of (see Bits.java).
That looks familiar. And yes, I see what you did there, and I don't
think Roger's initial prototype testing did anything similar, so
indeed this is likely the failure he encountered.
Though I'm still inclined to object to that form of drainQueue (see
below).
I don't understand why CleanerImpl needs to be changed to public in
order to provide access to the new drainQueue. Wouldn't it be better
to add Cleaner.drainQueue?
An interesting idea. But I don't know if such functionality is generally useful
enough to commit to it in a public API.
java.desktop:sun.java2d.Disposer.pollRemove seems to me to be
addressing an essentially similar requirement, with
java.desktop:sun.font.StrikeCache being the user of that API.
Of course, that's already got all the scaffolding for using phantom
references, and there's no need to rewrite it to use
java.lang.ref.Cleaner. But maybe there are others like this?
In any case, I really dislike the approach of exposing the CleanerImpl
object to get at this functionality.
Some of the other changes here don't seem related to the problem at
hand. ...
One thing that this change unfortunately requires is to get rid of lambdas and
method references in the implementation and dependencies of
java.land.ref.Cleaner API, because it gets used early in the boot-up sequence
when java.lang.invoke infrastructure is not ready yet.
Oh, right! Bootstrapping issues!
The alternative to CleanerCleanable is a no-op Runnable implementation passed
to PhantomCleanableRef constructor. …
OK. Now I understand.
Making CleanerImpl implement Runnable …
I'd be fine with this if the CleanerImpl wasn't exposed as part of the
drainQueue functionality.
------------------------------------------------------------------------------
src/java.base/share/classes/sun/nio/fs/NativeBuffer.java
76 Cleaner.Cleanable cleanable() {
77 return cleanable;
78 }
[pre-existing, but if we're changing things anyway...]
I'm kind of surprised by an accessor function (both here and in the
original code) rather than a cleanup function. Is there a use case
for anything other than buffer.cleanable().clean()?
It can't be, since both old Cleaner and new Cleanable have only got a single
method - clean().
So this could be replaced with
void clean() {
cleanable.clean();
}
To me, that seems better.
Similarly for the DirectBuffer interface.
This one is a critical method, used by various 3rd party softwares...
I want to cover my ears when people start talking about some of the
things that have done… OK.
