Cong Wang <xiyou.wangc...@gmail.com> writes:
> On Fri, Jun 26, 2020 at 3:46 PM Petr Machata <pe...@mellanox.com> wrote: >> >> A following patch introduces qevents, points in qdisc algorithm where >> packet can be processed by user-defined filters. Should this processing >> lead to a situation where a new packet is to be enqueued on the same port, >> holding the root lock would lead to deadlocks. To solve the issue, qevent >> handler needs to unlock and relock the root lock when necessary. >> >> To that end, add the root lock argument to the qdisc op enqueue, and >> propagate throughout. > > Hmm, but why do you pass root lock down to each ->enqueue()? > > You can find root lock with sch_tree_lock() (or qdisc_lock() if you don't > care about hierarchy), and you already have qdisc as a parameter of > tcf_qevent_handle(). I know, I wanted to make it clear that the lock may end up being used, instead of doing it "stealthily". If you find this inelegant I can push a follow-up that converts tcf_qevent_handle() to sch_tree_unlock().
