Bug 307571 – [macOS] imported/w3c/web-platform-tests/workers/SharedWorkerPerformanceNow.html is a flaky text failure

• Component: DOM
• Status: RESOLVED FIXED

[Diego De La Toba]

imported/w3c/web-platform-tests/workers/SharedWorkerPerformanceNow.html is a flaky text failure on Sequoia and Tahoe on both architectures. 


HISTORY:
https://results.webkit.org/?suite=layout-tests&test=imported%2Fw3c%2Fweb-platform-tests%2Fworkers%2FSharedWorkerPerformanceNow.html


DIFF:
--- /Volumes/Data/worker/Apple-Tahoe-Release-AppleSilicon-WK2-Tests/build/layout-test-results/imported/w3c/web-platform-tests/workers/SharedWorkerPerformanceNow-expected.txt
+++ /Volumes/Data/worker/Apple-Tahoe-Release-AppleSilicon-WK2-Tests/build/layout-test-results/imported/w3c/web-platform-tests/workers/SharedWorkerPerformanceNow-actual.txt
@@ -1,4 +1,3 @@
 
+FAIL performance.now() exists in shared workers and reports reasonable times assert_greater_than: Time in the worker should be positive expected a number greater than 0 but got 0
 
-PASS performance.now() exists in shared workers and reports reasonable times
-


DIFF URL:
https://build.webkit.org/results/Apple-Tahoe-Release-AppleSilicon-WK2-Tests/307256%40main%20(1592)/imported/w3c/web-platform-tests/workers/SharedWorkerPerformanceNow-pretty-diff.html


REPRODUCTION:
I was able to reproduce this on macOS Tahoe ToT with the following:

run-webkit-tests --force --release --no-retry --exit-after-n-failures=1 --iterations 1000 imported/w3c/web-platform-tests/workers/SharedWorkerPerformanceNow.html

I am going to mark expectations as pass fail while this pends investigation.

[Radar WebKit Bug Importer]

<rdar://problem/170159172>

[Diego De La Toba]

Pull request: https://github.com/WebKit/WebKit/pull/58421

[EWS]

Test gardening commit 307272@main (4b90c7d89e94): <https://commits.webkit.org/307272@main>

Reviewed commits have been landed. Closing PR #58421 and removing active labels.

[Diego De La Toba]

The error message is: "Time in the worker should be positive expected a number greater than 0 but got 0"
This looks like a test issue, not a WebKit issue. I believe the problem is when the SharedWorker executes very quickly, performance.now() can legitimately return 0 since there is a 1ms timer precision for performance.now()  (If the SharedWorker calls performance.now() within the first ~0.5ms of creation, it will round down to 0ms). According to the spec, performance.now() returning 0 is valid.

I am going to put this fix up as a PR, please review.

[Diego De La Toba]

Pull request: https://github.com/WebKit/WebKit/pull/58425

[EWS]

Committed 307405@main (30d1ac0d9651): <https://commits.webkit.org/307405@main>

Reviewed commits have been landed. Closing PR #58425 and removing active labels.

[Ryan Reno]

Was there a corresponding WPT pull request? If not, this change isn't slated to go upstream and will be overwritten the next time the suite is synced.