RFR: 8318757: VM_ThreadDump asserts in interleaved ObjectMonitor::deflate_monitor calls [v7]

[Stefan Karlsson]

> A safepointed monitor deflation pass can run interleaved with a paused async monitor deflation pass. The code is not written to handle that situation and asserts when it finds a DEFLATER_MARKER in the owner field. @pchilano also found other issues with having to monitor deflation passes interleaved. More info below ...

Stefan Karlsson has updated the pull request incrementally with three additional commits since the last revision:

 - Remove the limit for deflation requests
 - Remove reinitialization in test
 - Update comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16519/files
  - new: https://git.openjdk.org/jdk/pull/16519/files/103d917a..560c67df

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16519&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16519&range=05-06

  Stats: 24 lines in 5 files changed: 4 ins; 12 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/16519.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16519/head:pull/16519

PR: https://git.openjdk.org/jdk/pull/16519