260185 2023-08-14 17:26:02 -0700 REGRESSION(262173@main): media/media-source/media-source-fastseek.html is a flaky text failure 2023-08-29 11:11:41 -0700 1 1 1 Unclassified WebKit Media Other Unspecified Unspecified RESOLVED FIXED https://bugs.webkit.org/show_bug.cgi?id=259699 https://bugs.webkit.org/show_bug.cgi?id=250844 https://bugs.webkit.org/show_bug.cgi?id=260607 https://bugs.webkit.org/show_bug.cgi?id=260742 https://bugs.webkit.org/show_bug.cgi?id=260833 https://bugs.webkit.org/show_bug.cgi?id=260867 InRadar P2 Normal --- 1 ben_schwartz jean-yves.avenard jean-yves.avenard webkit-bot-watchers-bugzilla webkit-bug-importer oldest_to_newest 1971184 0 ben_schwartz 2023-08-14 17:26:02 -0700 media/media-source/media-source-fastseek.html This test is a flaky text failure on wk2 on macOS Monterey and above (EXCEPT on debug builds on x86_64 architecture). HISTORY: https://results.webkit.org/?suite=layout-tests&test=media%2Fmedia-source%2Fmedia-source-fastseek.html&flavor=wk2&version_name=Monterey&version_name=Ventura TEXT DIFF: EXPECTED (video.currentTime.toFixed(1) == '3') OK RUN(video.fastSeek(2)) EVENT(seeked) -EXPECTED (video.currentTime.toFixed(1) == '0') OK +EXPECTED (video.currentTime.toFixed(1) == '0'), OBSERVED '3.0' FAIL END OF TEST DIFF URL: https://build.webkit.org/results/Apple-Ventura-Release-AppleSilicon-WK2-Tests/266873@main%20(4437)/media/media-source/media-source-fastseek-diff.txt REPRODUCTION: I was able to reproduce this bug on macOS Monterey (x86_64) running the test as follows: run-webkit-tests --clobber-old-results --iterations 1000 --exit-after-n-failures 5 media/media-source/media-source-fastseek.html REGRESSION: I was able to bisect a regression point using the flakiness dashboard. This test reproduced at 262173@main, but it did not reproduce at 262172@main. Changes at 262173@main appear to be directly related to this error, and is likely what caused the failure. 1971185 1 webkit-bug-importer 2023-08-14 17:26:16 -0700 <rdar://problem/113881009> 1971190 2 ben_schwartz 2023-08-14 17:55:02 -0700 I have marked this test as a flaky failure while the issue is being investigated. (PR link: https://github.com/WebKit/WebKit/pull/16693) 1971191 3 ews-feeder 2023-08-14 17:56:48 -0700 Test gardening commit 266889@main (9544bcf5ae90): <https://commits.webkit.org/266889@main> Reviewed commits have been landed. Closing PR #16693 and removing active labels. 1971753 4 jean-yves.avenard 2023-08-17 00:09:17 -0700 I can see what the problem is: we assume that we have completed the seek when we have a signal that the time changed and that the player is not seeking. However, as soon as the RemoteMediaPlayer receives a timechange call, it assumes seeking has completed. That is not always the case: like if the GPU Process sent timechange just before we started seeking. 1971789 5 jean-yves.avenard 2023-08-17 03:46:56 -0700 fastSeek with MediaSource is broken as it is. When performing an accurate seek, the flow is to call MediaSourcePrivate::waitForSeekCompleted() , seek and then MediaSourcePrivate::seekCompleted(). between the two `waitForSeekCompleted` and `seekCompleted` `MediaPlayerPrivate::seeking` will return false. However, when doing a fast seek, we never call `MediaSourcePrivate::waitForSeekCompleted()` so `MediaPlayerPrivate::seeking` will return a stale value, which is typically the state of the previous seek and so typically `false` In this particular test, when we perform a `fastSeek` , if the GPU Process sent an earlier `timeChanged` as `MediaPlayerPrivate::seeking` will return `false` and so we fire `seeked` event even before the GPU Process has completed the seek operation and had time to update the currentTime to the actual value. I also note that in `void HTMLMediaElement::mediaPlayerTimeChanged()` we immediately call `updateActiveTextTrackCues(currentMediaTime());` but at this stage, currentMediaTime() returns the value of currentTime prior the seek operation. And as such it will set the TrackCues to the wrong time. 1972342 6 jean-yves.avenard 2023-08-21 03:44:04 -0700 It's actually a very similar failure to bug 250844. But while bug 250844 fixed it in just AVFObjC implementation, we can adopt a more global solution by making the entire seek operation an asynchronous operation with completion handlers. 1972964 7 jean-yves.avenard 2023-08-23 07:04:26 -0700 Pull request: https://github.com/WebKit/WebKit/pull/16974 1973522 8 ews-feeder 2023-08-25 07:17:47 -0700 Committed 267279@main (ee5de7a0c1f2): <https://commits.webkit.org/267279@main> Reviewed commits have been landed. Closing PR #16974 and removing active labels.