[jdk17u-dev] RFR: 8305425: Thread.isAlive0 doesn't need to call into the VM

Tue Jun 13 19:14:16 UTC 2023

Unclean backport to improve `Thread.isAlive` performance, and provide grounds for more backports in the area.

The majority of conflicts are due to integration of Loom in JDK 19, which reshaped some Thread code. I tried to change as little in 17u as possible to avoid the change fan-out.

Additional testing:
 - [x] Linux x86_64 fastdebug `tier1 tier2 tier3`
 - [x] Linux AArch64 fastdebug `tier1 tier2 tier3`

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Commit messages:
 - Adjust comment: drop the mention of non-existent FieldHolder
 - Touchups to minimize the difference
 - Backport 35cb303a2c0c8b32de257c02e012a1928a6b4594

Changes: https://git.openjdk.org/jdk17u-dev/pull/1425/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1425&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305425
  Stats: 141 lines in 7 files changed: 125 ins; 10 del; 6 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1425.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1425/head:pull/1425

PR: https://git.openjdk.org/jdk17u-dev/pull/1425