Integrated: 8311981: Test gc/stringdedup/TestStringDeduplicationAgeThreshold.java#ZGenerational timed out

[David Holmes]

On Fri, 11 Aug 2023 05:09:31 GMT, David Holmes <dholmes at openjdk.org> wrote:

> Please see the JBS issue for full details on the underlying deadlock issue (credit to @stefank for discovering it) and the proposed solution (credit @pchilano and @xmas92 ). Quite simply we make `HandshakeState::has_operation()` non-blocking by using a `try_lock` and conservatively return `true` to indicate an operation may be pending. By not blocking we avoid the deadlock scenario. All usages of the changed code have been examined to see that they are safe with this change (they all basically just take a safe slow path to see if there really is an operation).
> 
> Testing:
> - tiers 1-4, 7
> - the failing string dedup test was run under our tier7 conditions, 10 times on linux-x64-debug and windows-x64-debug
> 
> Given the nature of the deadlock this testing is not sufficient to claims success as we probably only saw 1 failure in many hundreds of runs. So if anyone has suggestions for additional testing please speak up. Otherwise we are relying on "correctness by design" - we've removed a blocking condition that leads to the 3-way deadlock, and examined the code paths affected.
> 
> Thanks.

This pull request has now been integrated.

Changeset: f142470d
Author:    David Holmes <dholmes at openjdk.org>
URL:       https://git.openjdk.org/jdk/commit/f142470deaebbf9cff7f6f28842972393506b7c4
Stats:     11 lines in 1 file changed: 9 ins; 0 del; 2 mod

8311981: Test gc/stringdedup/TestStringDeduplicationAgeThreshold.java#ZGenerational timed out

Reviewed-by: stefank, pchilanomate, dcubed, rehn

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PR: https://git.openjdk.org/jdk/pull/15240