Messages in this thread | | | Date | Thu, 3 Apr 2008 11:22:36 -0700 | From | "Paul Menage" <> | Subject | Re: [-mm] Add an owner to the mm_struct (v7) |
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On Thu, Apr 3, 2008 at 11:11 AM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > Hmm, is this new check for delay_group_leader() safe? Won't we have > > called exit_cgroup() by this point, and hence be reassigned to the > > root cgroup? And so mm->owner->cgroups won't point to the right place? > > > > cgroup_exit() comes in much later after exit_mm(). Moreover delay_group_leader() > is a function that checks to see if
Sorry, I was unclear.
Yes, the call to cgroup_exit() comes much later than exit_mm() - but it probably does come before the other users of the mm have finished using the mm. So can't we end up with a situation like this?
A (group leader) exits; at this point, A->mm->owner == A A calls exit_mm(), sees delay_group_leader(), doesn't change A->mm->owner A calls cgroup_exit(), A->cgroups is set to init_css_set. B (another thread) does something with B->mm->owner->cgroups (e.g. VM accounting) and accesses the wrong group
Paul
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