RFR: 8317433: Async UL: Only grab lock once when write():ing [v2]

[Johan Sjölen]

> Hi,
> 
> The writer thread used to await for `_data_available` to become true through using the async log lock as a condition variable. When data is available it'd let go of the lock and then call `AsyncLogWriter::write()`, which would immediately try to acquire that same lock. We can remove this second instance by moving the work needed to be done under lock to `run`.
> 
> Thank you for considering this.

Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:

  Switch to resource allocation

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16030/files
  - new: https://git.openjdk.org/jdk/pull/16030/files/fb8eca0d..7255fb12

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16030&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16030&range=00-01

  Stats: 4 lines in 2 files changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/16030.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16030/head:pull/16030

PR: https://git.openjdk.org/jdk/pull/16030