Public bug reported:
On a hardened, but empty system, where only few other processes are
running, maximum speed IO output to cryptoloop causeD kernel to get
stuck multiple times (~5x), e.g.
echo x | losetup -e aes-cbc-essiv:sha256 -k 256 --pass-fd 0 /dev/loop0 /dev/sda2
dd if=/dev/zero of=/dev/loop0
dd process cannot be terminated, also kill from other session does not
stop it. Process is stuck in
# cat /proc/11296/stack
[<c10eaa64>] balance_dirty_pages.clone.9+0x1e4/0x390
[<c10eac71>] balance_dirty_pages_ratelimited_nr+0x61/0x70
[<c10e190a>] generic_perform_write+0x14a/0x1b0
[<c10e19c4>] generic_file_buffered_write+0x54/0x90
[<c10e3910>] __generic_file_aio_write+0x220/0x4e0
[<c115389c>] blkdev_aio_write+0x3c/0xa0
[<c11269e4>] do_sync_write+0xa4/0xe0
[<c11271a2>] vfs_write+0xa2/0x170
[<c1127482>] sys_write+0x42/0x70
[<c1509bf4>] syscall_call+0x7/0xb
[<ffffffff>] 0xffffffff
CPU load reaches rather exactly 1 afterwards.
top - 13:09:21 up 2:41, 2 users, load average: 1.00, 0.99, 0.95
Tasks: 66 total, 1 running, 65 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.0%us, 0.0%sy, 0.0%ni, 24.9%id, 75.1%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1025224k total, 680820k used, 344404k free, 312772k buffers
Swap: 0k total, 0k used, 0k free, 240680k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
1 root 20 0 2896 796 384 S 0.0 0.1 0:01.45 init
The loop can be broken by power off/hard reboot BUT ALSO WITH
kill -KILL [pid]; echo t > /proc/sysrq-trigger.
The task listing does not contain the terminated process. Since I tried
the echo for the first time (echo 5h after hang), I do not know, if this
could be used to kill or fix the task in any case. I will try to do
further analysis when hang occurs again.
# lsb_release -rd
Description: Ubuntu 11.04
Release: 11.04
# apt-cache policy linux-image-2.6.38-8-generic
linux-image-2.6.38-8-generic:
Installed: 2.6.38-8.42
Candidate: 2.6.38-8.42
Version table:
*** 2.6.38-8.42 0
500 http://archive.ubuntu.com/ubuntu/ natty/main i386 Packages
100 /var/lib/dpkg/status
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/803525
Title:
Endless loop in balance_dirty_pages.clone.9 on cryptoloop
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