RFR: 8360048: NMT crash in gtest/NMTGtests.java: fatal error: NMT corruption: Block at 0x0000017748307120: header canary broken

[David Holmes]

This is a clone of https://github.com/openjdk/jdk/pull/25950 that we need to get integrated ASAP.

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The canary header test failed since there were concurrent remove and free() from the tree. The remove operations are synch'ed with corresponding NMT lock. The ReserveMemory::reserve() uses the same lock internally and is not included in the locked code block.

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I'm re-testing with tiers 1-4

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Commit messages:
 - Merge branch 'master' into 8360048-nmt
 - local VMT vs static one.
 - 8360048: NMT crash in gtest/NMTGtests.java: fatal error: NMT corruption: Block at 0x0000017748307120: header canary broken

Changes: https://git.openjdk.org/jdk/pull/26284/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26284&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8360048
  Stats: 126 lines in 5 files changed: 20 ins; 21 del; 85 mod
  Patch: https://git.openjdk.org/jdk/pull/26284.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26284/head:pull/26284

PR: https://git.openjdk.org/jdk/pull/26284