Long line of kisses locks up processor in Thunderbird

[Colin Law]

To replicate, send an email to Thunderbird client containing a line of 40,000 'x' characters, from a client that does not split the lines. In thunderbird attempt to reply to this email and it locks the processor at 100% for several minutes. I may be necessary to start typing into the reply to trigger the effect.
I have not tested to determine whether the fact that they are kisses embarrasses Thunderbird so that it gets all in a tizzy, or whether any long line would achieve the same effect.

Further information:
The problem is only seen when replying in text mode, reply in html format is ok.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: thunderbird 7.0.1+build1+nobinonly-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
Uname: Linux 3.0.0-12-generic i686
NonfreeKernelModules: nvidia
AddonCompatCheckDisabled: False
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 1.23-0ubuntu4
Architecture: i386
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: colinl 1359 F.... pulseaudio
BuildID: 20110929181644
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'NVidia'/'HDA NVidia at 0xf9ef8000 irq 20'
   Mixer name : 'Realtek ALC888'
   Components : 'HDA:10ec0888,14627369,00100001'
   Controls : 37
   Simple ctrls : 22
Channel: release
Date: Mon Nov 14 11:32:38 2011
ForcedLayersAccel: False
IfupdownConfig:
 auto lo
 iface lo inet loopback
InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release i386 (20111012)
IpRoute:
 default via 192.168.1.1 dev eth0 proto static
 169.254.0.0/16 dev eth0 scope link metric 1000
 192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.100 metric 1
IwConfig:
 lo no wireless extensions.

 eth0 no wireless extensions.
Profiles: Profile0 (Default) - LastVersion=7.0.1/20110929181644
RfKill:

RunningIncompatibleAddons: False
SourcePackage: thunderbird
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/20/2007
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: V2.4
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: MS-7369
dmi.board.vendor: MSI
dmi.board.version: 1.0
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrV2.4:bd11/20/2007:svnMSI:pnMS-7369:pvr1.0:rvnMSI:rnMS-7369:rvr1.0:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: MS-7369
dmi.product.version: 1.0
dmi.sys.vendor: MSI

[Alan Pope 🍺🐧🐱 🦄 (popey)]

Here's 40,000 kisses you can use when testing this bug report:-

http://paste.ubuntu.com/738131/

[Alan Pope 🍺🐧🐱 🦄 (popey)]

I couldn't reproduce this on 11.10.

[Colin Law (colin-law)]

I wonder whether it is the scrolling that triggers the problem. Are you able to type text *above* the message (top posting will be allowed for this test case).
Alternatively, in the original message the long line was itself top posted so the complete email filled the window, perhaps it is the scrolling in this case that caused the problem.
I will do some further tests myself.

[Colin Law (colin-law)]

Following further tests, to replicate start a Reply to the message, position cursor at start of message and hit enter. Each hit of enter causes a 40 second processor lockup.
@Alan, if that does not do it could you try it in plain text mode? I think from your screenshot you are in html. I can't work out how to set Thunderbird to html format to try that myself. It is probably hidden somewhere in plain sight.

[Colin Law (colin-law)]

I find that the problem is only seen when replying in text mode. Reply in html format is ok.
Use Shift Reply to engage the alternative mode of reply if configured for html.

[Alan Pope 🍺🐧🐱 🦄 (popey)]

Confirmed. In plain text mode almost any interaction with a window containing a large amount of un-splittable text will cause thunderbird to consume one CPU core and become unresponsive for tens of seconds.