[Bug 1325309] Re: User can't suspend laptop/control wireless via dbus/systemd-logind if cgroups are disabled in kernel

[Rob A]

Thanks Martin.

I confirmed that that single change in my .config restores proper
operation.

No it shouldn't affect power usage, but it's not used in BFS (which
isn't going to be mainline, I know), so I'm curious why suspend (and
NetworkManager) require it?  it seems to be completely unnecessary for
the functions I need.


Regarding the desktop: a few apps wouldn't connect to pulse-audio, but I wasn't sure what was causing that, or if Skype was broken again.  It turns out it was both this, and skype being broken again.

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Title:
  User can't suspend laptop/control wireless via dbus/systemd-logind if
  cgroups are disabled in kernel

Status in “systemd” package in Ubuntu:
  Invalid

Bug description:
  This is kind of a long chain, but I think this is where it ends.

  I custom compile my kernel for battery savings, as I spend lots of time flying. I recently went back to BFS in 3.14 as my scheduler, but immediately ran into lots of problems (it used to give me 15 more minutes on average).  The most interesting, that I can't work around is this:
  I disable cgroups because BFS doesn't use them at all.  and when I did, even with the ubuntu linux-source package, I suddenly couldn't put my laptop to sleep, and I couldn't control my network connections anymore.  Investigating lead me to discover that "start systemd-logind" was failing.

  So, here's my  relevant config:

  rob at kubuntu4:~$ grep CGROUP /boot/config-`uname -r`; sudo start systemd-logind; dmesg |tail -1; ls /sys/fs/cgroup
  # CONFIG_CGROUPS is not set
  start: Job failed to start
  [ 1450.848491] init: systemd-logind pre-start process (10865) terminated with status 32
  ls: cannot access /sys/fs/cgroup: No such file or directory

  the /sys/fs/cgroup folder doesn't exist because CONFIG_CGROUPS isn't
  set in the kernel.  So what is "status 32" from the pre-script for
  systemd-logind ?

  the problem seems to be in the mount statements in the systemd-logind
  prestart script:

  grep mount /etc/init/systemd-logind.conf 
      # this is being done by systemd or mountall usually, but not during
      if ! mountpoint -q /sys/fs/cgroup; then
          mount -t tmpfs -o uid=0,gid=0,mode=0755,size=1024 none /sys/fs/cgroup
      # mounting the cgroup does not work in LXC, there it uses cgmanager
      if [ ! -e /run/container_type ] && ! mountpoint -q /sys/fs/cgroup/systemd; then
          mount -t cgroup -o nosuid,noexec,nodev,none,name=systemd systemd /sys/fs/cgroup/systemd

  Testing: 
  sudo mount -t tmpfs -o uid=0,gid=0,mode=0755,size=1024 none /sys/fs/cgroup; echo $?
  [sudo] password for rob: 
  mount: mount point /sys/fs/cgroup does not exist
  32

  Rebooting into the stock ubuntu kernel, and I can put my laptop to
  sleep again, albeit at the cost of a bunch of battery life.

  I don't understand why cgroups are required for dbus and PolicyKit to
  be able to allow me to put my laptop to sleep, so I'm filing this as a
  bug.  the systemd pre-script doesn't bother to check if the
  /sys/fs/cgroup folder even exists, so there's definitely a "defensive
  programming" bug in systemd not handling this situation better.

  currently "sudo pm_suspend" is an easy workaround for the sleep issue,
  but my wireless access issue has no workaround.

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