Re: [PATCH 2/2] kthread, cgroup: close race window where new kthreads can be migrated to non-root cgroups

From	Tejun Heo <tj@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 2/2] kthread, cgroup: close race window where new kthreads can be migrated to non-root cgroups
Date	2017-03-16 18:50 +0100
Message-ID	<tlHHc-1ID-5@gated-at.bofh.it> (permalink)
References	(1 earlier) <tlqmZ-6ih-1@gated-at.bofh.it> <tlFvH-gv-9@gated-at.bofh.it> <tlFP5-pI-35@gated-at.bofh.it> <tlG8q-LZ-37@gated-at.bofh.it> <tlGBs-10m-29@gated-at.bofh.it>
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Hello,

On Thu, Mar 16, 2017 at 05:31:59PM +0100, Oleg Nesterov wrote:
> Or we can add another "unsigned no_cgroups:1" bit into task_struct,
> not sure.

To synchronize around initialization, a PF flag would be easier as we
can use wait_on_bit().

> Anyway, I do not understand the PF_NO_SETAFFINITY check in
> __cgroup_procs_write(). task_can_attach() checks it too, so cgroups
> can't change the affinity. Imo something explicit like no_cgroups
> makes more sense.

task_can_attach() predates the __cgroup_procs_write() and currently
doesn't do anything.  We can split the flag or rename it so that it's
more generic.  The reasons for disallowing cgroup migration have a lot
of crosssection with affinity, so it's not a complete misnomer.
Either way is fine by me.

Thanks.

-- 
tejun

Thread

[PATCH 2/2] kthread, cgroup: close race window where new kthreads  can be migrated to non-root cgroups Tejun Heo <tj@kernel.org> - 2017-03-16 00:20 +0100
  Re: [PATCH 2/2] kthread, cgroup: close race window where new         kthreads can be migrated to non-root cgroups Oleg Nesterov <oleg@redhat.com> - 2017-03-16 16:30 +0100
    Re: [PATCH 2/2] kthread, cgroup: close race window where new         kthreads can be migrated to non-root cgroups Oleg Nesterov <oleg@redhat.com> - 2017-03-16 16:50 +0100
      Re: [PATCH 2/2] kthread, cgroup: close race window where new  kthreads can be migrated to non-root cgroups Tejun Heo <tj@kernel.org> - 2017-03-16 17:10 +0100
        Re: [PATCH 2/2] kthread, cgroup: close race window where new         kthreads can be migrated to non-root cgroups Oleg Nesterov <oleg@redhat.com> - 2017-03-16 17:40 +0100
          Re: [PATCH 2/2] kthread, cgroup: close race window where new  kthreads can be migrated to non-root cgroups Tejun Heo <tj@kernel.org> - 2017-03-16 18:50 +0100
    Re: [PATCH 2/2] kthread, cgroup: close race window where new  kthreads can be migrated to non-root cgroups Tejun Heo <tj@kernel.org> - 2017-03-16 17:10 +0100
      Re: [PATCH 2/2] kthread, cgroup: close race window where new         kthreads can be migrated to non-root cgroups Oleg Nesterov <oleg@redhat.com> - 2017-03-16 17:30 +0100
        Re: [PATCH 2/2] kthread, cgroup: close race window where new  kthreads can be migrated to non-root cgroups Tejun Heo <tj@kernel.org> - 2017-03-16 18:20 +0100
  [PATCH v2] cgroup, kthread: close race window where new kthreads can  be migrated to non-root cgroups Tejun Heo <tj@kernel.org> - 2017-03-16 22:10 +0100
    Re: [PATCH v2] cgroup, kthread: close race window where new         kthreads can be migrated to non-root cgroups Oleg Nesterov <oleg@redhat.com> - 2017-03-17 15:00 +0100
      Re: [PATCH v2] cgroup, kthread: close race window where new kthreads  can be migrated to non-root cgroups Tejun Heo <tj@kernel.org> - 2017-03-17 15:50 +0100

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