Messages in this thread | | | Date | Thu, 13 Nov 2008 07:04:27 +0530 | From | Balbir Singh <> | Subject | Re: [RFC][mm] [PATCH 4/4] Memory cgroup hierarchy feature selector (v3) |
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Li Zefan wrote: >> + /* >> + * 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; >
Hi, Li,
I thought I had the cgroup_lock() around that check, but I seemed to have missed it. I'll fix that in v4.
-- Balbir
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