[crac] RFR: RCU Lock - RW lock with very lightweight read- and heavyweight write-locking [v6]

[Radim Vansa]

> This implementation is suitable for uses where the write-locking happens very rarely (if at all), as in the case of CRaC checkpoint, and we don't want to slow down regular access to the protected resource.

Radim Vansa has updated the pull request incrementally with one additional commit since the last revision:

  Add forgotten condition.signal() call

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Changes:
  - all: https://git.openjdk.org/crac/pull/58/files
  - new: https://git.openjdk.org/crac/pull/58/files/1116ace6..984cb5d3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=58&range=05
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=58&range=04-05

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/crac/pull/58.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/58/head:pull/58

PR: https://git.openjdk.org/crac/pull/58