On Fri, Jun 26, 2020 at 3:46 PM Petr Machata [off-list ref] wrote:

The function tcf_qevent_handle() should be invoked when qdisc hits the
"interesting event" corresponding to a block. This function releases root
lock for the duration of executing the attached filters, to allow packets
generated through user actions (notably mirred) to be reinserted to the
same qdisc tree.

Are you sure releasing the root lock in the middle of an enqueue operation
is a good idea? I mean, it seems racy with qdisc change or reset path,
for example, __red_change() could update some RED parameters
immediately after you release the root lock.

Thanks.