On Mon, Sep 11, 2017 at 2:14 PM, Cong Wang <xiyou.wangc...@gmail.com> wrote:
>
> Looks like all due to the lack of locking on block->chain_list.
> I thought the rcu_barrier() could properly handle this,
> but seems still not, probably I need to move it in the loop,
> I am still not 100% sure if it is totally safe with
> list_for_each_safe():
>
>
> - list_for_each_entry(chain, &block->chain_list, list)
> + list_for_each_entry_safe(chain, tmp, &block->chain_list, list) {
> tcf_chain_flush(chain);
> - rcu_barrier();
> + rcu_barrier(); // are we safe now???
> + }
>
Answer myself: No, this is not safe either, because we may
list_del() the next node, and apparently _safe() can't guarantee
that...
So either we have to use locking or use the trick you suggested.
