Re: [PATCH v3 16/19] KVM: MMU: lockless walking shadow page table

Marcelo Tosatti
2011-07-07T08:51:30Z

On Thu, Jul 07, 2011 at 03:26:14AM +0800, Xiao Guangrong wrote:
> On 07/07/2011 02:08 AM, Marcelo Tosatti wrote:
>
> >> +static void free_pages_rcu(struct rcu_head *head)
> >> +{
> >> + struct kvm_mmu_page *next, *sp;
> >> +
> >> + sp = container_of(head, struct kvm_mmu_page, rcu);
> >> + while (sp) {
> >> + if (!list_empty(&sp->link))
> >> + next = list_first_entry(&sp->link,
> >> + struct kvm_mmu_page, link);
> >> + else
> >> + next = NULL;
> >> + kvm_mmu_free_page(sp);
> >> + sp = next;
> >> + }
> >> +}
> >
> > There is no need for this while loop.
> >
>
> The while loop is needed, since many shadow pages can be freed together in
> the rcu context, on commit_zap_page path, we only remove the list head, and
> the shadow page is still listed.

Right.