RFR: 8373100: Genshen: Control thread can miss allocation failure notification

[William Kemper]

In some cases, the control thread may fail to observe an allocation failure. This results in the thread which failed to allocate waiting forever for the control thread to run a cycle. Depending on which thread fails to allocate, the process may not make progress.

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Commit messages:
 - Expand scope of control lock so that it can't miss cancellation notifications

Changes: https://git.openjdk.org/jdk/pull/28665/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28665&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373100
  Stats: 8 lines in 1 file changed: 2 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/28665.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28665/head:pull/28665

PR: https://git.openjdk.org/jdk/pull/28665