1403035 - Intermittent async-scrolling/checkerboard-2-ref.html | assertion count 1 is more than expected 0 assertions from ASSERTION: Tried to delete invalid animation: 'Error'

Status: VERIFIED FIXED

(Core :: Graphics: WebRender, defect, P1)

Description

[Treeherder Bug Filer]

Filed by: philringnalda [at] gmail.com

https://treeherder.mozilla.org/logviewer.html#?job_id=133222021&repo=autoland

https://queue.taskcluster.net/v1/task/clnxM9C0Rjy1qjbXg_Ue5Q/runs/0/artifacts/public/logs/live_backing.log

https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/reftest-analyzer.xhtml#logurl=https://queue.taskcluster.net/v1/task/clnxM9C0Rjy1qjbXg_Ue5Q/runs/0/artifacts/public/logs/live_backing.log&only_show_unexpected=1

Comment 1

[Kartikaya Gupta (email:[e-mail])]

Probably a regression from bug 1402439. Based on the occurrences it looks like it only started after bug 1402439 merged to m-c so likely it interacted with some other change to cause this.

Comment 2

[Kartikaya Gupta (email:[e-mail])]

So far no luck reproducing this locally. I did a lot of runs of this reftest both individually and with the entire folder, with rr chaos mode.

Comment 3

[Kartikaya Gupta (email:[e-mail])]

Still can't repro locally. Pushed a logging patch to try: https://treeherder.mozilla.org/#/jobs?repo=try&revision=481fa4e1ce54afe1fdc336330946c5c51df1cec3

Comment 4

[Kartikaya Gupta (email:[e-mail])]

I was able to repro on try with logging applied. Somehow we're sending a nonzero id from the content side over to the parent side for discard, and the parent doesn't know about the id. Here's the relevant snippet:

WebRenderAnimationData adding id 0x44c0000005e for discard
WRLM(0) adding 0x44c0000005e for discard
REFTEST TEST-LOAD | file:///builds/worker/workspace/build/tests/reftest/tests/layout/reftests/async-scrolling/checkerboard-2.html | 1467 / 1956 (75%)
++DOMWINDOW == 57 (0x7faacc8de000) [pid = 1100] [serial = 3518] [outer = 0x7faad07a2000]
WRLM(0) discarding animations
WRBP trying erase of id 0x44c0000005e
!!! WRBP tried to delete invalid animation 0x44c0000005e

This id (0x44c0000005e) is not referenced anywhere else in the output. So what I believe is happening is that we are creating the id at [1] because that's the only call that goes through EnsureAnimationsId without logging something. And then when the WebRenderAnimationData object associated with that frame is destroyed, it schedules the id for discard. However, the id should be getting ignored in WebRenderLayerManager::AddCompositorAnimationsIdForDiscard [2], because the id doesn't exist in mActiveCompositorAnimationIds.

I think the problem is that we're actually going into the layers-full branch at [3], which bypasses the mActiveCompositorAnimationIds check. And the reason we're going into the layers-full branch is because the reftest harness keeps flipping the layers-free pref to true at the start of each individual test and then back to false after the test. So there's opportunity for race conditions where if the WebRenderAnimationData object is destroyed in between one of the pref flips, then it will take the layers-full codepath.

Once we turn layers-free on by default and remove the "default-preferences" annotation in the reftest.list file, this problem should go away.

[1] http://searchfox.org/mozilla-central/rev/f6dc0e40b51a37c34e1683865395e72e7fca592c/layout/painting/nsDisplayList.cpp#6578
[2] https://hg.mozilla.org/mozilla-central/file/b30ae5a45536/gfx/layers/wr/WebRenderLayerManager.cpp#l1018
[3] https://hg.mozilla.org/mozilla-central/file/b30ae5a45536/gfx/layers/wr/WebRenderLayerManager.cpp#l1013

Comment 5

[Vincent Liu[:vliu]]

Hi Peter,
Do you think this bug is relatives to bug 1396471?

Comment 6

[Kartikaya Gupta (email:[e-mail])]

See comment 4.

Comment 7

[Kartikaya Gupta (email:[e-mail])]

And yes, this seems to have stopped after landing bug 1389000.

https://brasstacks.mozilla.com/orangefactor/?display=Bug&bugid=1403035&startday=2017-09-20&endday=2017-09-27&tree=trunk

Comment 8

[Intermittent Failures Robot]

12 failures in 885 pushes (0.014 failures/push) were associated with this bug in the last 7 days.    

Repository breakdown:
* autoland: 5
* mozilla-inbound: 4
* mozilla-central: 2
* try: 1

Platform breakdown:
* linux64-qr: 12

For more details, see:
https://brasstacks.mozilla.com/orangefactor/?display=Bug&bugid=1403035&startday=2017-09-25&endday=2017-10-01&tree=all

Comment 9

[Kartikaya Gupta (email:[e-mail])]

OF shows this is down to zero.