Messages in this thread | | | Date | Thu, 13 Nov 2008 09:28:23 +0800 | From | Li Zefan <> | Subject | Re: [RFC][mm] [PATCH 4/4] Memory cgroup hierarchy feature selector (v3) |
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> + /* > + * If parent's use_hiearchy is set, we can't make any modifications > + * in the child subtrees. If it is unset, then the change can > + * occur, provided the current cgroup has no children. > + * > + * For the root cgroup, parent_mem is NULL, we allow value to be > + * set if there are no children. > + */ > + if (!parent_mem || (!parent_mem->use_hierarchy && > + (val == 1 || val == 0))) { > + if (list_empty(&cont->children)) > + mem->use_hierarchy = val; > + else > + retval = -EBUSY; > + } else > + retval = -EINVAL; > + > + return retval; > +}
As I mentioned there is a race here. :(
echo 1 > /memcg/memory.use_hierarchy =>if (list_empty(&cont->children)) mkdir /memcg/0 => mem->use_hierarchy = 0 mem->use_hierarchy = 1;
Now it ends up with parent's use_hierarchy is set but its child's use_hierarchy is not set.
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