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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