nft_hash rhashtable question

Hi Thomas,

I'm looking at the rhashtable usage.

But as I read the nft_hash_destroy() its not clear to me how
rht_for_each_entry_safe() and  nft_hash_elem_destroy() keep everything
in sync.

Here is the code in question,

static void nft_hash_destroy(const struct nft_set *set)
{
        struct rhashtable *priv = nft_set_priv(set);
        const struct bucket_table *tbl;
        struct nft_hash_elem *he;
        struct rhash_head *pos, *next;
        unsigned int i;

        /* Stop an eventual async resizing */
        priv->being_destroyed = true;
        mutex_lock(&priv->mutex); <-- get the lock so we have single updater

        tbl = rht_dereference(priv->tbl, priv);
        for (i = 0; i < tbl->size; i++) {
                rht_for_each_entry_safe(he, pos, next, tbl, i, node)
                        nft_hash_elem_destroy(set, he);              <-- does a kfree on he?
        }
        mutex_unlock(&priv->mutex); <-- release the lock

        rhashtable_destroy(priv);
}

Is it really safe to kfree 'he' without waiting a grace
period for any rcu readers to drop the reference?

I'm considering what happens if nft_hash_destroy runs in
parallel with nft_hash_lookup?

Thanks,
John


-- 
John Fastabend         Intel Corporation