We don't need jdk.internal.ref.Cleaner any more

[Chris Hegarty]

On 8 Feb 2016, at 06:27, Alan Bateman <Alan.Bateman at oracle.com> wrote:

> 
> On 07/02/2016 22:20, Peter Levart wrote:
>> :
>> 
>> If the decision to remove sun.misc.Cleaner was partly influenced by the desire to maintain just 2 instead of 3 Cleaner(s), then my proposal to migrate JDK code to the public API might enable Oracle to reconsider keeping sun.misc.Cleaner.
> 
> The main issue driving this is the design principles that we have listed in JEP 200. We don't want a standard module (java.base in this case) exporting a non-standard API. This means surgery to jettison the sun.misc package from java.base and move it to its own module (jdk.unsupported is the proposal in JEP 260). This is painful of course but we are at least in good shape for the most critical internal API, sun.misc.Unsafe.
> 
> For sun.misc.Cleaner then the original proposal was for it to be a critical internal API too but it become clear that changing the type of internal/private fields in the NIO buffer and channel classes would break libraries that have been hacking into those fields. If they are changing away then there seems little motive to keep sun.misc.Cleaner so Chris moved into into jdk.internal.ref for now. As to whether we even need to keep jdk.internal.ref.Cleaner then I think the only remaining question was whether the special handling of Cleaner in the Reference implementation was worth it or not. It may not be, in which case your current proposal to just remove seems right.

Alan’s summary of the situation is spot on.

Before moving sun.misc.Cleaner to jdk.internal.ref, I did enquire if it would be 
possible to just remove it and use the new public Cleaner, but I got feedback
that there were some issues with failing NIO tests ( it appeared that Cleaners
were not running as quickly as possible ). I didn’t look further into that at the
time, since the VM still had special knowledge of these cleaners, but as you
say this is now removed.  It is probably a good time to revisit this.

-Chris.