firefox is pegging 2 CPUs at nearly 100%

[Colin Ian King]

Top is showing that 2 CPUs are being consumed at nearly 100% each:

  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
 3916 king 20 0 1160372 264036 50188 S 198.7 4.5 36:54.78 firefox

Seems like it is spinning in pthread_cond_wait()

(gdb) where
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185
#1 0x00007fefa1de3f28 in PR_WaitCondVar () from /usr/lib/firefox/libnspr4.so
#2 0x00007fefa1de4218 in PR_Wait () from /usr/lib/firefox/libnspr4.so
#3 0x00007fef9dfdd172 in ?? () from /usr/lib/firefox/libxul.so
#4 0x00007fef9dfde17d in ?? () from /usr/lib/firefox/libxul.so
#5 0x00007fef9e99e0ae in ?? () from /usr/lib/firefox/libxul.so
#6 0x00007fef9e99e0cd in ?? () from /usr/lib/firefox/libxul.so
#7 0x00007fef9dfa421b in ?? () from /usr/lib/firefox/libxul.so
#8 0x00007fef9e99e387 in ?? () from /usr/lib/firefox/libxul.so
#9 0x00007fef9e99e3c3 in ?? () from /usr/lib/firefox/libxul.so
#10 0x00007fef9dfbf2b6 in ?? () from /usr/lib/firefox/libxul.so
#11 0x00007fef9dfbf88a in ?? () from /usr/lib/firefox/libxul.so
#12 0x00007fef9dfa70a0 in ?? () from /usr/lib/firefox/libxul.so
#13 0x00007fef9eeba08f in ?? () from /usr/lib/firefox/libxul.so
#14 0x00007fef9eebe940 in ?? () from /usr/lib/firefox/libxul.so
#15 0x00007fef9eebeb5a in XRE_main () from /usr/lib/firefox/libxul.so
#16 0x00007fefa33503c1 in _start ()
(gdb) quit

..and looks like it's possibly spinning on a futex

System calls traced:
  PID Process Syscall Count Rate/Sec Total μSecs % Call Time
  3916 firefox futex 1 0.0167 0 0.0000

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: firefox 28.0+build1-0ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-16.36-lowlatency 3.13.5
Uname: Linux 3.13.0-16-lowlatency x86_64
AddonCompatCheckDisabled: False
ApportVersion: 2.13.3-0ubuntu1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: king 3531 F.... pulseaudio
BrokenPermissions:
 sessionstore.bak (0o600, wrong owner)
 sessionstore.js (0o600, wrong owner)
BuildID: 20140313141126
Channel: Unavailable
CurrentDesktop: Unity
Date: Sat Mar 15 16:32:27 2014
EcryptfsInUse: Yes
ForcedLayersAccel: False
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
IncompatibleExtensions:
 English (GB) Language Pack - <email address hidden>
 English (South Africa) Language Pack - <email address hidden>
 Default - {972ce4c6-7e08-4474-a285-3208198ce6fd}
InstallationDate: Installed on 2013-12-09 (95 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20131209)
IpRoute:
 default via 192.168.0.1 dev eth0 proto static
 192.168.0.0/24 dev eth0 proto kernel scope link src 192.168.0.14 metric 1
 192.168.0.0/24 dev wlan0 proto kernel scope link src 192.168.0.20 metric 9
 192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1
MostRecentCrashID: bp-77eb6b98-c032-4092-a561-b70f22130104
PrefSources: prefs.js
Profiles: Profile0 (Default) - LastVersion=28.0/20140313141126
RelatedPackageVersions:
 rhythmbox-mozilla 3.0.1-1ubuntu15
 google-talkplugin 5.1.5.0-1
 totem-mozilla 3.10.1-1ubuntu3
RfKill:
 0: phy0: Wireless LAN
  Soft blocked: no
  Hard blocked: no
RunningIncompatibleAddons: True
SourcePackage: firefox
UpgradeStatus: No upgrade log present (probably fresh install)
WifiSyslog: Mar 15 16:30:27 lenovo kernel: [ 1278.310072] ptrace of pid 3916 was attempted by: gdb (pid 5412)
dmi.bios.date: 05/24/2012
dmi.bios.vendor: LENOVO
dmi.bios.version: G2ET31WW (1.11 )
dmi.board.asset.tag: Not Available
dmi.board.name: 2320CTO
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrG2ET31WW(1.11):bd05/24/2012:svnLENOVO:pn2320CTO:pvrThinkPadX230:rvnLENOVO:rn2320CTO:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 2320CTO
dmi.product.version: ThinkPad X230
dmi.sys.vendor: LENOVO

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Anders Hall (a.hall)]

Hi, i can almost say that this is the same problem I have. I also run Lenovo x230 and often experience 50 to 100% Firefox utilization (currently Firefox 29, Ubuntu 14.04) on various tabs (i.e., is not related to a specific site). I will post proper debug info/dump during the spike as soon as it happens again. I have seen variants of this since 12.04 at least and also on x201.

I have tested html5 video performance, and other problems areas, at Mozilla where Firefox 27 to 31 has know bugs. However, in this case video processes are not related, even considered that CPU spikes occur in those cases as well.

Notable difference for me vs Colin is that Firefox sometimes hangs in a weird way during this CPU spike. I can use the current Firefox window, even open new tabs and surf etc. However, if i close Firefox during this process with the CPU spike then the Firefox process is not killed, i need to manually kill it. A "plugin container" process seem to also stay open.

Any commands to get more debug info/dump in this situation is welcome?