[CRIU] [PATCH] Skip restoring certain cgroup root directories when using full mode

[Andrew Vagin]

On Wed, Aug 26, 2015 at 11:12:02PM -0400, Hui Kang wrote:
> On Wed, Aug 26, 2015 at 12:27 AM, Andrew Vagin <avagin at gmail.com> wrote:
> > On Tue, Aug 25, 2015 at 10:25:02PM -0400, Hui Kang wrote:
> >>
> >> Hi, Pavel
> >> I still have difficulty in producing the bug you described. I have
> >> /sys/fs/cgroup/cpuset (which is the root) and /sys/fs/cgroup/cpuset/A.
> >> I have added task 1001 to the root and 1002 to
> >> /sys/fs/cgroup/cpuset/A. The patch has no problem in restoring the the
> >> task in /A.
> >>
> >> If this is the not nested case you described, could you give more
> >> detailed about the case you think of? Thanks.
> >
> > I think I've reproduced this bug:
> > https://asciinema.org/a/cv3qlitwvvt2guyi2woaok056
> 
> Hi, Andew,
> I created my own script to reproduce the bug of not restoring cpu
> share. The script is
> 
> #! /bin/bash
> set -e -x
> echo $$
> mkdir -p /sys/fs/cgroup/cpu/A
> echo 512 > /sys/fs/cgroup/cpu/A/cpu.shares
> sleep 1000 &
> echo $! > /sys/fs/cgroup/cpu/A/tasks
> wait
> [ `cat /sys/fs/cgroup/cpu/A/cpu.shares` -ne 512 ] && echo FAIL
> 
> It will create two pid, say the first is 18001 and the second is 18002.
> When I run
> 
> criu dump -t 18001 -vvvv --log-file dump.log -j  --manage-cgroup=ful
> 
> It gives me the error
> 
> Dumping file-locks
> (00.028444)
> (00.028451) Dumping pstree (pid: 18672)
> (00.028458) ----------------------------------------
> (00.028466) Process: 18672(18672)
> (00.028506) Process: 18674(18674)
> (00.028516) ----------------------------------------
> (00.028619) Error (cgroup.c:807): cg: Non supported sub-cgroups found
> (00.028961) Unlock network
> (00.028983) Unfreezing tasks into 1
> (00.028994) Unseizing 18672 into 1
> (00.029081) Unseizing 18674 into 1
> 
> I am using the criu from git. Do you know why this happens? Thanks.

I have seen this error too.
CRIU and the root task live in the same set of cgroups.
CRIU expects that all task should live in this set of cgroups.
Pavel, could you explain this behaviour?

        /*
         * Check whether root task lives in its own set as compared
         * to criu. If yes, we should not dump anything, but make
         * sure no other sets exist. The latter case can be supported,
         * but requires some trickery and is hardly needed at the
         * moment.
         */

        if (root_cgset == criu_cgset) {
                if (!list_is_singular(&cg_sets)) {
                        pr_err("Non supported sub-cgroups found\n");
                        return -1;
                }


> 
> - Hui
> 
> >
> >>
> >> - Hui
> >>
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