RFR: 8351996: Behavioral updates for ClassValue::remove [v10]
Viktor Klang
vklang at openjdk.org
Wed Apr 30 09:16:50 UTC 2025
On Tue, 29 Apr 2025 19:03:08 GMT, Chen Liang <liach at openjdk.org> wrote:
>> 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 17 additional commits since the last revision:
>
> - Rewrite impl to follow the new simplified spec
> - Merge branch 'master' of https://github.com/openjdk/jdk into fix/classvalue-compute-remove
> - Try to simplify the model - use the finish of computeValue
>
> - Test updates - remove repetition, test case for no stale installation
> - Fix incorrect promise removal when unnecessary and add regression test
> - Cannot test for recursion eagerly - add test case
> - More spec, eager exception, finish with existing, thanks John
> - Merge branch 'master' of https://github.com/openjdk/jdk into fix/classvalue-compute-remove
> - docs
> - Remove the throwing behavior due to shallow reentrancy
> - ... and 7 more: https://git.openjdk.org/jdk/compare/bde12d99...221d51e7
src/java.base/share/classes/java/lang/ClassValue.java line 89:
> 87: * not attempt to associate a value, and may terminate either by returning
> 88: * an observed associated value, if it exists, or by propagating that
> 89: * exception.
Does this mean that exceptions may be swallowed?
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/24043#discussion_r2068233456
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