Messages in this thread | | | Date | Tue, 9 Apr 2013 08:42:49 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH 1/8] cgroup: implement cgroup_is_ancestor() |
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On Mon 08-04-13 14:36:46, Tejun Heo wrote: > On Mon, Apr 08, 2013 at 08:03:44PM +0200, Michal Hocko wrote: > > __mem_cgroup_same_or_subtree relies on css_is_ancestor if hierarchy is > > enabled for ages. This, however, is not correct because use_hierarchy > > doesn't need to be true all the way up the cgroup hierarchy. Consider > > the following example: > > root (use_hierarchy=0) > > \ > > A (use_hierarchy=0) > > \ > > B (use_hierarchy=1) > > \ > > C (use_hierarchy=1) > > > > __mem_cgroup_same_or_subtree(A, C) would return true even though C is > > not from the same hierarchy subtree. The bug shouldn't be critical but > > at least dump_tasks might print unrelated tasks (via > > task_in_mem_cgroup). > > Huh? Isn't that avoided by the !root_memcg->use_hierarchy test?
Yes, it is. My selective blindness strikes again :/ I was convinced that it was memcg we tested use_hierarchy for... Sorry about all the churn.
> > @@ -1470,9 +1470,12 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, > > { > > if (root_memcg == memcg) > > return true; > > - if (!root_memcg->use_hierarchy || !memcg) > ^^^^^^^^^^^^^^^^^^^^^^^^^^ > > + if (!memcg) > > return false; > > - return css_is_ancestor(&memcg->css, &root_memcg->css); > > + while ((memcg = parent_mem_cgroup(memcg))) > > + if (memcg == root_memcg) > > + return true; > > + return false; > > } > > -- Michal Hocko SUSE Labs
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