Comment 0 for bug 1265841

In my attempts to find an easy way to reproduce this bug:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1265684
... I actually found a very simple way to trigger a bug that is similar but not identical. I suspect that both bugs have the same cause: something in the kernel is disabling IRQs and the ext4 code will crash when this happens.

The stack trace for this bug is different from the other one. This one appears to be less severe, the system is still usable after the crash, only the process that caused the crash will hang (uninterruptible sleep).

This bug is 100% reproducible on both Ubuntu 13.10 with kernel 3.11.0 and Arch Linux with kernel 3.12.6.

STEPS TO REPRODUCE
------------------

The steps to reproduce the bug are based on this:
http://www.spinics.net/lists/linux-ext4/msg38949.html

* Set up an ecryptfs 'Private' folder in your home directory.

* In that directory, create a file called 'crashme.c' with the following code in it:

#include <assert.h>
int main() { assert(0); }

* Compile the program:

gcc -Wall crashme.c -o crashme

* Change the core dump pattern so core dumps are saved in the current directory:

echo "coredump-%p" | sudo tee /proc/sys/kernel/core_pattern

* Enable core dumps:

ulimit -c unlimited

* Make sure that you have a second terminal open to run dmesg, because you may not be able to do so later.

* Run 'crashme' - this will hang and trigger the bug:

./crashme

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: linux-image-3.11.0-15-generic 3.11.0-15.23
ProcVersionSignature: Ubuntu 3.11.0-15.23-generic 3.11.10
Uname: Linux 3.11.0-15-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 2.12.5-0ubuntu2.2
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: maarten 1666 F.... lxpanel
CRDA: Error: [Errno 2] No such file or directory: 'iw'
Date: Fri Jan 3 15:58:24 2014
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=bc17e234-da75-457f-b17c-22d9c0e27dd8
InstallationDate: Installed on 2013-12-28 (6 days ago)
InstallationMedia: Lubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
IwConfig:
 eth0 no wireless extensions.

 lo no wireless extensions.
MachineType: Gigabyte Technology Co., Ltd. Z87X-D3H
MarkForUpload: True
ProcFB: 0 EFI VGA
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.11.0-15-generic.efi.signed root=UUID=5a8ae1fc-91bf-4ce0-8dea-a519976fd56b ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.11.0-15-generic N/A
 linux-backports-modules-3.11.0-15-generic N/A
 linux-firmware 1.116
RfKill:

SourcePackage: linux
StagingDrivers: zram
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/02/2013
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: F7
dmi.board.asset.tag: To be filled by O.E.M.
dmi.board.name: Z87X-D3H-CF
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrF7:bd08/02/2013:svnGigabyteTechnologyCo.,Ltd.:pnZ87X-D3H:pvrTobefilledbyO.E.M.:rvnGigabyteTechnologyCo.,Ltd.:rnZ87X-D3H-CF:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.name: Z87X-D3H
dmi.product.version: To be filled by O.E.M.
dmi.sys.vendor: Gigabyte Technology Co., Ltd.