[lxc-devel] [PATCH 2/2] split cgroup handling into discrete backends

[Dwight Engen]

On Thu, 6 Feb 2014 10:49:22 -0600
Serge Hallyn <serge.hallyn at ubuntu.com> wrote:

> Quoting Dwight Engen (dwight.engen at oracle.com):
> > On Wed, 5 Feb 2014 23:34:16 -0600
> > Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> > 
> > > Quoting Serge Hallyn (serge.hallyn at ubuntu.com):
> > > > Quoting Dwight Engen (dwight.engen at oracle.com):
> > > > > - refactor cgroup into two backends, the classic cgfs driver
> > > > > and the new cgmanager. Instead of lxc_handler knowing about
> > > > > the internals of each, have it just store an opaque pointer
> > > > > to a struct that is private to each backend.
> > > > > 
> > > > > - rename a couple of cgroup functions for consistency: those
> > > > > that are considered an API (ie. exported by lxc.h) begin with
> > > > > lxc_ and those that are not are just cgroup_*
> > > > > 
> > > > > - made as many backend routines static as possible, only
> > > > > cg*_ops_init is exported
> > > > > 
> > > > > - made a nrtasks op which is needed by the utmp code for
> > > > > monitoring container shutdown, currently only implemented for
> > > > > the cgfs backend
> > > > 
> > > > Hi Dwight,
> > > > 
> > > > boy this diff got into some unfortunate strides (with
> > > > near-identical code being removed then inserted pages later)
> > > > making it harder to read than necessary :)
> > > > 
> > > > > Signed-off-by: Dwight Engen <dwight.engen at oracle.com>
> > > > 
> > > > Acked-by: Serge E. Hallyn <serge.hallyn at ubuntu.com>
> > > > 
> > > > (I'll apply after I run some tests)
> > > 
> > > Unfortunately, while containers started fine, lxc-attach and
> > > lxc-cgroup no longer seemed to work.  If it isn't obvious to
> > > you what the problem migth be, I'll look into it tomorrow.
> > 
> > Hmm, thats strange. I tested both of those with both backends. I'll
> > try to reproduce it here. I also tested the shutdown while frozen
> > case and at first I thought it was broken but then I realized that
> > you just have to wait for the timeout to occur (which is the same
> > as it used to be).
> 
> Works now, not sure what I did last night.
> 
> Pushed - thanks.
> 
> -serge

Hey Serge,

I do have one more question: do we expect that cgmanager will only be
used with a kernel that supports reboot(2) for container shutdown? (ie.
kernel commit 923c7538). Looks like this has been in since 3.9.

I ask because I tested that the utmp watch stuff still works for cgfs,
but obviously it doesn't right now with cgmanager since the nrtasks op
isn't filled in.