RFR: 8351996: Behavioral updates for ClassValue::remove [v2]

Chen Liang liach at openjdk.org
Wed Mar 19 21:35:53 UTC 2025


> The recent patch #23866 makes calling `ClassValue::remove()` from `ClassValue::computeValue()` end up in infinite loops while fixing the stale value risk from the method.
> 
> The proposed fix is to preserve the stale value risk fix, and update the remove-from-compute behavior from the original designated no-op behavior to throwing an exception, as the original behavior conflicts with the stale value fix.
> 
> The implementation track the owner thread in promises (accessed in locked section); as a result, we can fail-fast on recursive removals from `computeValue`. I did not choose to use `ThreadTracker` as it is designed for single tracker and multiple threads, while this case here sees often just one thread, and the threads outlive the promise objects.
> 
> Also updated the API specs for `remove` to more concisely describe the memory effects. Please review the associated CSR as well.

Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Use identity of thread, some optimizations for single thread case
 - Merge branch 'master' of https://github.com/openjdk/jdk into fix/classvalue-compute-remove
 - Track threads on the promise for cheap reentrancy checks
 - 8351996: Alternative way to ensure no stale values for ClassValue::remove

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24043/files
  - new: https://git.openjdk.org/jdk/pull/24043/files/70bf2368..74851320

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24043&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24043&range=00-01

  Stats: 14260 lines in 293 files changed: 7595 ins; 4232 del; 2433 mod
  Patch: https://git.openjdk.org/jdk/pull/24043.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24043/head:pull/24043

PR: https://git.openjdk.org/jdk/pull/24043


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