Paul Rouget [:paul] Assignee
	Description • 9 years ago

My terminal is flooded with this warning:

[Parent 46797] WARNING: Dropping task posted to controller thread: file ./gfx/layers/apz/util/APZThreadUtils.cpp, line 70

It happens every time I scroll inside a remote iframe.

Configuration:
- B2G Desktop
- APZC enabled
- OSX
- scrolling with the trackpad


Is there anything I can do to help figuring out what's going on?

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 1 • 9 years ago

Do you have layers.async-pan-zoom.separate-event-thread set to true? If so set it back to false. Also make sure your build has bug 1148868. If you still see it then add logging at http://hg.mozilla.org/mozilla-central/annotate/754579ec0e68/widget/cocoa/nsChildView.mm#l1925 to see what is happening during startup.

	Paul Rouget [:paul] Assignee
	Comment 2 • 9 years ago

(In reply to Kartikaya Gupta (email:kats@mozilla.com) from comment #1)
> Do you have layers.async-pan-zoom.separate-event-thread set to true? If so
> set it back to false. Also make sure your build has bug 1148868.

It was set to false. And the patches from bug 1148868 were included.

> If you
> still see it then add logging at
> http://hg.mozilla.org/mozilla-central/annotate/754579ec0e68/widget/cocoa/
> nsChildView.mm#l1925 to see what is happening during startup.

Apparently, this function is never called.

In nsBaseWidget::CreateCompositor(), IsMultiProcessWindow() is false, so ConfigureAPZCTreeManager() is never called.

If I force IsMultiProcessWindow to true, nsBaseWidget::ConfigureAPZControllerThread() is called, but as soon as I try scrolling in a child process, it freezes.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 3 • 9 years ago

We are only allowing APZ in e10s windows. If IsMultiProcessWindow is false the window is non-e10s, so APZ should not have been activated. Can you get a backtrace to the warning you reported in comment 0? Nothing should be calling that code if APZ is not activated.

	Paul Rouget [:paul] Assignee
	Comment 4 • 9 years ago

Some context:

- this is a special build of B2G Desktop (https://hg.mozilla.org/projects/larch)
- "layers.async-pan-zoom.enabled" -> true
- the window hierarchy is:

  . native cocoa window, (b2g/shell.html)
    . html:iframe non-remote mozbrowser mozapp, (app/index.html)
      . html:iframe remote mozbrowser, (http://cnn.com)

- the last iframe is inside a overflowing div that has the attribute scrollgrab.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 5 • 9 years ago

Oh fun. Yet another combination of platforms that we didn't properly account for. This one is cocoa widget (so we do the e10s check) but has e10s disabled (so we don't set up APZ in the parent process). However TabChild just checks the pref and not if it's an e10s child process or a remote mozbrowser process so it thinks APZ is enabled. Hence the mismatch and error. Let me figure out how we want to handle this case.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 6 • 9 years ago

So for now I think you should be ok to locally take out the IsMultiProcessWindow check (which I moved to CompositorParent yesterday in bug 1162179) so that APZ is enabled in your non-e10s windows. The freezing you were seeing in comment 2 was likely bug 1161040 and should be fixed in central. Let me know if you still have problems with that.

	Paul Rouget [:paul] Assignee
	Comment 7 • 9 years ago

Appears to work well now.

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 8 • 9 years ago

Comment on attachment 8603252 [details] [diff] [review]
v1

Review of attachment 8603252 [details] [diff] [review]:
-----------------------------------------------------------------

Please update the comment inside the ifdef to explicitly mention the use of moz_b2g instead of moz_widget_gonk to capture b2g desktop environments.

	Paul Rouget [:paul] Assignee
	Comment 9 • 9 years ago

Updated comment.

	Paul Rouget [:paul] Assignee
	Comment 10 • 9 years ago

https://treeherder.mozilla.org/#/jobs?repo=try&revision=f242cf189510

	Kartikaya Gupta (email:kats@mozilla.staktrace.com)
	Comment 11 • 9 years ago

https://hg.mozilla.org/integration/mozilla-inbound/rev/0a2cfe0345f0

	Carsten Book [:Tomcat]
	Comment 12 • 9 years ago

https://hg.mozilla.org/mozilla-central/rev/0a2cfe0345f0