1212136 - 5,100 instances of "Attempting to get a margins-based displayport with no base data!" emitted from layout/base/nsLayoutUtils.cpp during linux64 debug testing

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

[Eric Rahm [:erahm]]

This is the #1 most verbose warning during testing and appears to be a recent e10s regression.

> 5144 [NNNNN] WARNING: Attempting to get a margins-based displayport with no base data!: file layout/base/nsLayoutUtils.cpp, line 884

This warning [1], introduced in bug 1001438, shows up in the following test suites:

> mozilla-central_ubuntu64_vm-debug_test-reftest-e10s-1-bm123-tests1-linux64-build26.txt:1845
> mozilla-central_ubuntu64_vm-debug_test-reftest-e10s-2-bm118-tests1-linux64-build54.txt:1677
> mozilla-central_ubuntu64_vm-debug_test-crashtest-e10s-bm53-tests1-linux64-build14.txt:548
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-browser-chrome-6-bm118-tests1-linux64-build6.txt:315
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-1-bm68-tests1-linux64-build7.txt:205
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-browser-chrome-7-bm118-tests1-linux64-build4.txt:177
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-2-bm123-tests1-linux64-build7.txt:82
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-5-bm123-tests1-linux64-build9.txt:68
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-browser-chrome-3-bm68-tests1-linux64-build48.txt:61
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-3-bm118-tests1-linux64-build41.txt:48
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-browser-chrome-1-bm68-tests1-linux64-build1.txt:45
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-4-bm68-tests1-linux64-build10.txt:38
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-browser-chrome-5-bm53-tests1-linux64-build7.txt:16
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-browser-chrome-4-bm53-tests1-linux64-build12.txt:13
> mozilla-central_ubuntu64_vm-debug_test-mochitest-e10s-browser-chrome-2-bm123-tests1-linux64-build41.txt:6

It shows up in     3842 tests. A few of the most prevalent:

> 43 - browser/components/sessionstore/test/browser_formdata_cc.js
> 41 - Shutdown
> 33 - browser/base/content/test/general/browser_overflowScroll.js
> 28 - dom/manifest/test/browser_ManifestObtainer_obtain.js
> 27 - browser/base/content/test/general/browser_tabMatchesInAwesomebar.js
> 25 - dom/tests/mochitest/bugs/test_bug346659.html
> 24 - file:///builds/slave/test/build/tests/reftest/tests/layout/reftests/svg/as-image/img-fragment-1a.html
> 24 - file:///builds/slave/test/build/tests/reftest/tests/layout/reftests/bugs/421710-1.html
> 24 - dom/html/test/test_iframe_sandbox_navigation2.html
> 18 - docshell/test/navigation/test_sessionhistory.html

[1] https://hg.mozilla.org/mozilla-central/annotate/780f34be1855+/layout/base/nsLayoutUtils.cpp#l884

Comment 1

[Eric Rahm [:erahm]]

Sorry, a functioning link:
[1] https://hg.mozilla.org/mozilla-central/annotate/89732fcdb0baca70e8b7a25a2725117113f0db80/layout/base/nsLayoutUtils.cpp#l884

Comment 2

[Daniel Holbert [:dholbert]]

hg blame (comment 1) says kats added this warning. ni=him to comment on its usefulness / worrisomeness here.

Comment 3

[Eric Rahm [:erahm]]

(In reply to Daniel Holbert [:dholbert] from comment #2)
> hg blame (comment 1) says kats added this warning. ni=him to comment on its
> usefulness / worrisomeness here.

Note: The warning was added in 2014, the log spam regression is recent (last few weeks). Also note: kats is out for a couple of weeks.

Comment 4

[Timothy Nikkel (:tnikkel)]

The log spam regression was probably caused when apz was enabled on linux recently.

Comment 5

[Eric Rahm [:erahm]]

(In reply to Timothy Nikkel (:tn) from comment #4)
> The log spam regression was probably caused when apz was enabled on linux
> recently.

Confirmed, the log spam first appeared when bug 1143856 merged to m-c on 9/30.

Comment 6

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

I've seen this warning crop up occasionally in real-world usage too and suspect that there are legitimate code paths that end up triggering this warning. I've never seen any user-visible harmful effect when this warning is printed. So I'm happy to have the warning removed until we have cycles to properly investigate (i.e. never). Feel free to assign the bug to me if you'd like me to do that.

Comment 7

[Eric Rahm [:erahm]]

(In reply to Kartikaya Gupta (email:[e-mail]) from comment #6)
> I've seen this warning crop up occasionally in real-world usage too and
> suspect that there are legitimate code paths that end up triggering this
> warning. I've never seen any user-visible harmful effect when this warning
> is printed. So I'm happy to have the warning removed until we have cycles to
> properly investigate (i.e. never). Feel free to assign the bug to me if
> you'd like me to do that.

Doesn't sound like there are any objections to removal.

Comment 8

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

Attachment: Silence warning

Comment 9

[Timothy Nikkel (:tnikkel)]

Comment on attachment 8680759 [details] [diff] [review]
Silence warning

When we added that I thought we'd hit it in some rare cases. But being a giant spam like this I did not expect. I'd like to investigate to see if some of our assumptions were incorrect and we hit it in the common case. Of course I can investigate whether or not it's spamming the logs.

Comment 10

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

Sounds good. Flagging for checkin since the tree is closed.

Comment 11

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/c80170938685

Comment 12

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/c80170938685

Comment 13

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/releases/mozilla-b2g44_v2_5/rev/c80170938685

Comment 14

[Carsten Book [:Tomcat]]

removing the b2g 2.5 flag since this commit has been reverted due to an incorrect merge, sorry for the confusion