DirectByteBuffers are still using old `jdk.internal.ref.Cleaner` implementation. That implementation carries a doubly-linked list, and so makes DBB suffer from the same issue fixed for generic `java.lang.ref.Cleaner` users with [JDK-8343704](https://bugs.openjdk.org/browse/JDK-8343704). See the bug for the reproducer.
We can migrate DBBs to use `java.lang.ref.Cleaner`. There are two pecularities during this rewrite. First, the old ad-hoc `Cleaner` implementation used to exit the VM when cleaning action failed. I presume it was to avoid memory leak / accidental reuse of the buffer. I moved the relevant block to `Deallocator` directly. Unfortunately, I cannot easily test it. Second is quite a bit hairy. Old DBB cleaning code was hooked straight into `Reference` processing loop. This was possible because we could infer that the weak references we are processing are in DBB cleaning action, since old `Cleaner` was the only use of this code. With standard `Cleaner`, we have lost this association, and so we cannot really do this from the reference processing loop. With the patched version, we now rely on normal `Cleaner` thread to do cleanups for us. Because of this, there is a new outpacing opportunity window where reference processing might have been over, but cleaner thread has not reacted yet. Tests show that DirectBufferAlloc tests are still surviving this, possibly due to exponential sleep-backoff already built in. See the reclamation path in `Bits.unreserveMemory`: https://github.com/openjdk/jdk/blob/c207cc7e705d3f449f2387324d86cfb31ce40c44/src/java.base/share/classes/java/nio/Bits.java#L106-L186 Additional testing: - [x] Linux x86_64 server fastdebug, `java/nio java/io` - [x] Linux AArch64 server fastdebug, `java/nio java/io` - [ ] Linux x86_64 server fastdebug, `all` - [ ] Linux AArch64 server fastdebug, `all` ------------- Commit messages: - Cleaner does not accept null cleanables - Fix Changes: https://git.openjdk.org/jdk/pull/22165/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22165&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8344332 Stats: 270 lines in 8 files changed: 15 ins; 234 del; 21 mod Patch: https://git.openjdk.org/jdk/pull/22165.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/22165/head:pull/22165 PR: https://git.openjdk.org/jdk/pull/22165
