Public bug reported:
I was testing how LXC runs a vivid systemd container on a vivid systemd
host and occasionally ended up with the container init getting stuck in
Ds state.
As this was happening rather frequently, I ended up stracing the container
systemd, which resulted in:
open("/sys/fs/cgroup/systemd/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_RDONLY|O_CLOEXEC) = 16
fstat(16, {st_mode=S_IFREG|0644, st_size=63, ...}) = 0
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0x7f350bdd0000
read(16, "5337\n5339\n5978\n5980\n5981\n5982\n59"..., 4096) = 62
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
access("/sys/fs/cgroup/devices", F_OK) = 0
open("/sys/fs/cgroup/devices/lxc/test-cont/system.slice/ssh.service/cgroup.procs",
O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC, 0666) = -1 ENOENT (No such file or
directory)
read(16,
fd 16:
lr-x------ 1 root root 64 Mar 7 18:37 16 ->
/sys/fs/cgroup/systemd/lxc/test-cont/system.slice/ssh.service/cgroup.procs
Next I noticed the bash autocompletion freezing on /var/lib on the host, so I
tried to ls /var/lib which froze too. Attaching strace on ls caused:
ls: cannot access /var/lib/lxcfs: Interrupted system call
running lxcfs processes:
root 759 0.6 0.0 22052 2748 ? Ss 15:31 1:16 /usr/bin/lxcfs
-f -s -o allow_other /var/lib/lxcfs/
root 6541 0.0 0.0 22052 448 ? S 18:30 0:00 /usr/bin/lxcfs
-f -s -o allow_other /var/lib/lxcfs/
root 6543 0.0 0.0 22052 448 ? S 18:30 0:00 /usr/bin/lxcfs
-f -s -o allow_other /var/lib/lxcfs/
attaching strace to them showed:
759: wait4(6541,
6541: wait4(6543,
6543: recvmsg(5,
fd5:
lrwx------ 1 root root 64 Mar 7 19:01 5 -> socket:[2082333]
netstat:
unix 3 [ ] DGRAM 2082333 -
@0572f
here I ran out of debugging ideas and decided to SIGKILL 6543, which
unfroze the container.
ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: lxcfs 0.6-0ubuntu2
Uname: Linux 3.19.0-031900rc7-generic x86_64
ApportVersion: 2.16.2-0ubuntu1
Architecture: amd64
Date: Sat Mar 7 19:44:18 2015
EcryptfsInUse: Yes
ProcEnviron:
TERM=screen
PATH=(custom, no user)
LANG=de_DE.UTF-8
LANGUAGE=en_US.UTF-8
SHELL=/bin/bash
SourcePackage: lxcfs
UpgradeStatus: Upgraded to vivid on 2013-03-06 (731 days ago)
** Affects: lxcfs (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug vivid
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https://bugs.launchpad.net/bugs/1429442
Title:
lxcfs can freeze systemd in a container
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