Messages in this thread | | | Date | Fri, 04 Apr 2008 00:04:39 +0530 | From | Balbir Singh <> | Subject | Re: [-mm] Add an owner to the mm_struct (v7) |
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Paul Menage wrote: > 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
Hi, Paul,
That is indeed quite bad. Do we have to retire the group_leader to init_css_set? Can we not check for delay_group_leader() there?
-- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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