Re: [PATCH v1 3/3] cgroup: relax common ancestor restriction for direct descendants

On Thu, 2016-07-21 at 11:26 -0400, Tejun Heo wrote:

Hello, James.

On Thu, Jul 21, 2016 at 08:16:34AM -0700, James Bottomley wrote:

quoted

quoted

That'd be one side.  The other side is the one moving.  Let's say 
the system admin thing wants to move all processe from A proper 
to B.   It would do that by draining processes from A's procs 
file into B's and even that is multistep and can race.

So the second part is that once we allow the creation of
subdirectories, there's no unified tasks file, so there's no way of
draining A proper without enumerating and descending into the 
cgroupns created subtrees in A?

Not that.  If it races, it will end up moving processes which are no
longer in A proper.

So if I as the cgroup ns owner am moving a task from A to A_subdir, the
admin scanning tasks in all of A may miss this task in motion because
all the tasks files can't be scanned atomically?

James