On Fri, Oct 19, 2018 at 05:46:28PM +0800, Qu Wenruo wrote:
> Did you mean some like this is possible?
>
> rbtree_postorder_for_each_entry_safe() {
> kfree(entry);
> }
>
> If so, I still don't really believe it's OK.
>
> For the following tree:
> 4
> / \
> 2 6
> / \ / \
> 1 3 5 7
>
> If current entry is 2, next is 3.
> And 2 get freed.
> Then we go 3, to reach next we need to go back to access 2, which is
> already freed, we will trigger use-after-free.
>
> So the only correct way to free the whole rbtree is still that tried and
> true while(rb_first()) loop.
>
> Or did I miss something?
It's postorder traversal so the node is ready for processing after all
it's children are processed. In the above example, it will result in the
followin sequence: 1 3 2 5 7 6 4 .
The iterator is safe in the sense that there's enough information saved
before going to the node so it's not needed to be accessed later, eg.
after it's freed.
prelim_release uses the same postorder/kfree pattern.
