Description of problem: When playing a full-screen video in the background and switching to an e10s-enabled Firefox, open tabs blank out. Version-Release number of selected component (if applicable): firefox-55.0.2-3.fc26 How reproducible: Always. Steps to Reproduce: 1. Open any number of tabs in Firefox and nagivate to a website in each. 2. Play a video in "mpv -vo opengl -fullscreen". 3. Alt+Tab to Firefox. Actual results: All open tabs turn blank. The pages that were loaded can still be navigated (e.g. clicking hyperlinks works when pointing the mouse to the right portion of the screen) but the pages (or any other pages navigated to) are not shown in the tab. When switching to another tab and then switching back, a spinning wheel appears. New tabs opened after starting to play the video are not affected. The following messages appear on stderr: IPDL protocol error: Handler returned error code! ###!!! [Parent][DispatchAsyncMessage] Error: PLayerTransaction::Msg_ReleaseLayer Processing error: message was deserialized, but the handler returned false (indicating failure) Expected results: All tabs should work as they did before starting the full-screen video. Additional info: I am using an Intel Corporation HD Graphics 620 graphics processor using the i965 X.org DRI driver.
That may be caused by https://bugzilla.mozilla.org/show_bug.cgi?id=1386279 You can try to run ff as "MOZ_DISABLE_CONTENT_SANDBOX=1 firefox" to disable sandbox to verify that.
The effect is the same with MOZ_DISABLE_CONTENT_SANDBOX=1.
Can you attach backtrace of the crash? How-to is here: https://fedoraproject.org/wiki/Firefox
There doesn't appear to be a crash as such. "firefox -g -d gdb" doesn't throw me onto a gdb prompt at any time after the initial "run", and neither does a gdb that I've manually attached to the content process with gdb -p (when running with the sandbox disabled).
Yes, debugging the remote e10s processes is tricky but we need that backtrace - there's no other way. You can also enable core dumps and then load the core to gdb. Look at https://mikeconley.ca/blog/2014/04/25/electrolysis-debugging-child-processes-of-content-for-make-benefit-glorious-browser-of-firefox/ to get some help.
The procedure described in the blog post is not much different from what I had done previously and following it directly leads to the same result: there doesn't appear to be a crash as such, the tab appears to blank out for some other reason. (And, like I've described, a broken tab remains functional despite being blank: I can click on links where they are supposed to be in the blank page and Firefox will request the new page, render it, and allow me to further click on links. It is simply that the page contents are not displayed and instead I get a blank page with a spinning wheel.) If I don't disable the content sandbox, the content process gdb does frequently break on SIGSYS signals (e.g. when the process attempts to open a file), but this seems to me to be simply the mechanism by which the sandbox usually operates if gdb isn't interfering and also happens before I trigger the bug.
I see. When you don see the message "This tab crashes" it's not a crash. It may be https://bugzilla.mozilla.org/show_bug.cgi?id=1377950
Ah, yes, that seems very likely. Certain compositing features such as window transparency do not work when I play a video full-screen, so it stands to reason that compositing is disabled in that situation.
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