Bug 158320 – LayoutTest tiled-drawing/scrolling/latched-div-with-scroll-snap.html is flaky

• Component: New Bugs
• Status: RESOLVED FIXED

[Ryan Haddad]

LayoutTest tiled-drawing/scrolling/latched-div-with-scroll-snap.html is flaky

This test is frequently failing or timing out on mac-wk2. It has been flaky for a while, but as of 5/28/16 it fails much more frequently.

Most recent failure:
<https://build.webkit.org/builders/Apple%20El%20Capitan%20Debug%20WK2%20(Tests)/builds/5581>

<https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=tiled-drawing%2Fscrolling%2Flatched-div-with-scroll-snap.html>

--- /Volumes/Data/slave/elcapitan-debug-tests-wk2/build/layout-test-results/tiled-drawing/scrolling/latched-div-with-scroll-snap-expected.txt
+++ /Volumes/Data/slave/elcapitan-debug-tests-wk2/build/layout-test-results/tiled-drawing/scrolling/latched-div-with-scroll-snap-actual.txt
@@ -3,7 +3,7 @@
 PASS div honored snap points.
 Testing that latch moves to bottom div:
 PASS top div did not move.
-PASS div scrolled to next window.
+FAIL div did not honor snap points. Expected 200, but got 50
 PASS successfullyParsed is true
 
 TEST COMPLETE

[Ryan Haddad]

El Capitan only, seems to fail 100% of the time

https://build.webkit.org/builders/Apple%20El%20Capitan%2032-bit%20JSC%20(BuildAndTest)?numbuilds=50

[Ryan Haddad]

(In reply to comment #1)
> El Capitan only, seems to fail 100% of the time
> 
> https://build.webkit.org/builders/Apple%20El%20Capitan%2032-
> bit%20JSC%20(BuildAndTest)?numbuilds=50

This comment was intended for a different bug. Please disregard.

However, tiled-drawing/scrolling/latched-div-with-scroll-snap.html is still frequently failing or timing out on Mac, especially on El Capitan Debug WK2

[Brent Fulgham]

(In reply to comment #2)
> (In reply to comment #1)
> > El Capitan only, seems to fail 100% of the time
> > 
> > https://build.webkit.org/builders/Apple%20El%20Capitan%2032-
> > bit%20JSC%20(BuildAndTest)?numbuilds=50
> 
> This comment was intended for a different bug. Please disregard.
> 
> However, tiled-drawing/scrolling/latched-div-with-scroll-snap.html is still
> frequently failing or timing out on Mac, especially on El Capitan Debug WK2

We have general flakiness in a lot of these scroll-snap/latching tests. Much of this is due to generating 'fake' wheel gestures to drive the tests. Maybe some partial event state is getting held over from test-to-test and causing things to behave in weird ways.

Simon and I spent a lot of time trying to get this more stable, but clearly more effort is needed.

[Alexey Proskuryakov]

> It has been flaky for a while, but as of 5/28/16 it fails much more frequently.

Is there any way to more precisely isolate when this started?

There were sweeping changes to callOnMainThread and NoncopyableFunction on 5/28 and 5/27, and while I don't see anything wrong with those patches, a mistake there could easily cause such symptoms.

[Alexey Proskuryakov]

It started early on 5/28, roughly around 1am. <http://trac.webkit.org/projects/webkit/changeset/201482> seems to fit.

[Alexey Proskuryakov]

Or looking at revision numbers and not at times, <http://trac.webkit.org/projects/webkit/changeset/201476>.

[Alexey Proskuryakov]

Marked as flaky in <http://trac.webkit.org/r202269>.

Zalan, do you think that you could look into this?

[alan]

Created attachment 281771 [details]
Patch

[Alexey Proskuryakov]

Comment on attachment 281771 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=281771&action=review

r=me pending EWS

> LayoutTests/tiled-drawing/scrolling/latched-div-with-scroll-snap.html:30
> -        <script src="../../resources/js-test.js"></script>
> +        <script src="../../resources/js-test-pre.js"></script>

Why this change? I think that js-test.js is slightly preferable in general.

[Alexey Proskuryakov]

Comment on attachment 281771 [details]
Patch

Please remove the test from TestExpectations, now that it's expected to pass reliably.

[alan]

Created attachment 281787 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 281787 [details]
Patch

Clearing flags on attachment: 281787

Committed r202304: <http://trac.webkit.org/changeset/202304>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.