Re: [PATCH net-next] net: sched: remove redundant 'rtnl_held' argument

[Vlad Buslov]

On Tue 01 Dec 2020 at 04:52, Jakub Kicinski <k...@kernel.org> wrote:
> On Fri, 27 Nov 2020 17:12:05 +0200 Vlad Buslov wrote:
>> @@ -2262,7 +2260,7 @@ static int tc_del_tfilter(struct sk_buff *skb, struct 
>> nlmsghdr *n,
>>  
>>      if (prio == 0) {
>>              tfilter_notify_chain(net, skb, block, q, parent, n,
>> -                                 chain, RTM_DELTFILTER, rtnl_held);
>> +                                 chain, RTM_DELTFILTER);
>>              tcf_chain_flush(chain, rtnl_held);
>>              err = 0;
>>              goto errout;
>
> Hum. This looks off.

Hi Jakub,

Prio==0 means user requests to flush whole chain. In such case rtnl lock
is obtained earlier in tc_del_tfilter():

        /* Take rtnl mutex if flushing whole chain, block is shared (no qdisc
         * found), qdisc is not unlocked, classifier type is not specified,
         * classifier is not unlocked.
         */
        if (!prio ||
            (q && !(q->ops->cl_ops->flags & QDISC_CLASS_OPS_DOIT_UNLOCKED)) ||
            !tcf_proto_is_unlocked(name)) {
                rtnl_held = true;
                rtnl_lock();
        }