Messages in this thread | | | Date | Wed, 19 Jan 2011 13:10:43 +0100 | From | Johannes Weiner <> | Subject | Re: [PATCH 2/4] memcg: fix USED bit handling at uncharge in THP |
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Hello KAMEZAWA-san,
On Tue, Jan 18, 2011 at 11:40:49AM +0900, KAMEZAWA Hiroyuki wrote: > +void mem_cgroup_split_huge_fixup(struct page *head, struct page *tail) > +{ > + struct page_cgroup *head_pc = lookup_page_cgroup(head); > + struct page_cgroup *tail_pc = lookup_page_cgroup(tail); > + unsigned long flags; > + > + /* > + * We have no races witch charge/uncharge but will have races with > + * page state accounting. > + */ > + move_lock_page_cgroup(head_pc, &flags); > + > + tail_pc->mem_cgroup = head_pc->mem_cgroup; > + smp_wmb(); /* see __commit_charge() */
I thought the barriers were needed because charging does not hold the lru lock. But here we do, and all the 'lockless' read-sides do so as well. Am I missing something or can this barrier be removed?
Hannes
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