[Bug 1856624] [NEW] Firefox freezes temporarily at 100% CPU when Chromium is opened

ais523 ais523 at nethack4.org
Tue Dec 17 00:51:27 UTC 2019

Public bug reported:

When Firefox is open, and I open Chromium, many features of Firefox fail
to work for several seconds. (To reproduce, start with neither Firefox
nor Chromium open; open Firefox, and allow one or more web pages to
load; then open Chromium; the issue starts a second or two after
Chromium is opened.) This is a temporary issue, lasting for several
seconds; the length of time it lasts appears to depend on how many open
tabs have been viewed since Firefox opened (on my computer, around 10
seconds with 1 tab having been viewed, around a minute with 10 tabs
having been viewed). This reproduces even when running Firefox as
`firefox -safe-mode`.

While the issue is ongoing (i.e. starting around a second after Chromium is open, and persisting for typically tens of seconds), some features of Firefox work, but most do not:
- Scrolling the current tab short distances succeeds, showing the expected text on the page.
- Scrolling the current tab long distances (several screeenfuls) causes the page to be "cut off" past a certain point, with only a blank background rendering.
- Moving the mouse cursor over a link does not change the mouse cursor (expected behaviour, and behaviour while the issue is not ongoing, is for it to change to a hand shape).
- Changing tab causes the resulting page not to display: rather, a grey background is displayed, and sometimes a loading spinner.
- Changing tab back then causes the original page not to render, as if it were new, despite the fact it was correctly displayed earlier.
- The address bar functions as normal; the issue does not appear to affect address bar functionality.
Additionally, while the issue is ongoing, Firefox uses 100% CPU.

At some point after the issue in question starts, it stops, and all
Firefox features return to normal (including any missing or incorrectly
rendered page content, which renders again when the issue ends).

The trigger is specifically the act of opening Chromium: Firefox can
function just fine once the issue ends, even if Chromium is still open,
and functions just fine if Chromium is opened first.

I have an (unconfirmed) theory that opening Chromium is causing some
operation within Firefox to become very slow, using up all the CPU time,
and the other observed misbehaviours within Firefox are a consequence of
how slowly it is running; however, I've listed them all anyway in case
it provides clarity into what the specific nature of the bug is.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: firefox 71.0+build5-0ubuntu0.18.04.1
ProcVersionSignature: Ubuntu 5.0.0-37.40~18.04.1-generic 5.0.21
Uname: Linux 5.0.0-37-generic x86_64
AddonCompatCheckDisabled: False
ApportVersion: 2.20.9-0ubuntu7.9
Architecture: amd64
 /dev/snd/controlC0:  ais523     1800 F.... pulseaudio
BuildID: 20191205184924
Channel: Unavailable
CurrentDesktop: X-Cinnamon
Date: Tue Dec 17 00:29:10 2019
ExecutablePath: /usr/lib/firefox/firefox
ForcedLayersAccel: False
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
 English (South Africa) Language Pack - langpack-en-ZA at firefox.mozilla.org
 Fran├žais Language Pack - langpack-fr at firefox.mozilla.org
 English (GB) Language Pack - langpack-en-GB at firefox.mozilla.org
 Default - {972ce4c6-7e08-4474-a285-3208198ce6fd}
InstallationDate: Installed on 2019-11-11 (35 days ago)
InstallationMedia: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
 default via dev wlp2s0 proto dhcp metric 600 dev wlp2s0 scope link metric 1000 dev wlp2s0 proto kernel scope link src metric 600
MostRecentCrashID: bp-935fd166-3720-454f-8fe5-0a1752140227
PrefErrors: Unexpected character ',' before close parenthesis @ /usr/lib/firefox/omni.ja:greprefs.js:722
PrefSources: prefs.js
 PATH=(custom, user)
Profiles: Profile0 (Default) - LastVersion=71.0/20191205184924 (In use)
RunningIncompatibleAddons: True
SourcePackage: firefox
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 05/30/2019
dmi.bios.vendor: Dell Inc.
dmi.bios.version: 1.5.1
dmi.board.name: 0DDKKC
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 10
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvr1.5.1:bd05/30/2019:svnDellInc.:pnInspiron3583:pvr:rvnDellInc.:rn0DDKKC:rvrA00:cvnDellInc.:ct10:cvr:
dmi.product.family: Inspiron
dmi.product.name: Inspiron 3583
dmi.product.sku: 08CA
dmi.sys.vendor: Dell Inc.

** Affects: firefox (Ubuntu)
     Importance: Undecided
         Status: New

** Tags: amd64 apport-bug bionic

You received this bug notification because you are a member of Mozilla
Bugs, which is subscribed to firefox in Ubuntu.

  Firefox freezes temporarily at 100% CPU when Chromium is opened

To manage notifications about this bug go to:

More information about the Ubuntu-mozillateam-bugs mailing list