RFR: 8280438: Improve BufferNode::Allocator::release to avoid walking pending list [v3]

[Kim Barrett]

> Please review this change to BufferNode::Allocator::release to avoid needing
> to walk the pending list in preparation for transferring it to the free list.
> We need to have both the head and the tail of the pending list to perform that
> transfer.
> 
> Rather than using a LockFreeStack to accumulate the pending list, we now use a
> bespoke data structure that only supports concurrent additions, since that's
> all we need.  This simplifies the code, and also makes it easy to capture the
> first pushed node as the tail.
> 
> To make the transfer from the pending list to the free list, we double-buffer
> the pending list.  Additions are made to the currently active pending list.  A
> transfer flips which pending list is active, and transfers from the list that
> was just deactivated.  Additions are made in a critical section.  The critical
> section synchronization already performed when transferring now does double
> duty, also synchronizing the pending list flip.
> 
> Testing:
> mach5 tier1-3
> 
> Ran a test with -Xlog:gc,ptrqueue,freelist and verified transfers were
> occurring as expected.

Kim Barrett has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Merge branch 'master' into buffer_release
 - update copyrights
 - change _pending_lists init for compiler bug workaround
 - double-buffer pending list

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7210/files
  - new: https://git.openjdk.java.net/jdk/pull/7210/files/70c52abb..b08a9cf6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7210&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7210&range=01-02

  Stats: 15843 lines in 685 files changed: 10584 ins; 2771 del; 2488 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7210.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7210/head:pull/7210

PR: https://git.openjdk.java.net/jdk/pull/7210