netdev - Re: [PATCH net-next v1 2/5] net: sched: Introduce helpers for qevent blocks

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Message-ID: <CAM_iQpXvwPGz=kKBFKQAkoJ0hwijC9M03SV9arC++gYBAU5VKw@mail.gmail.com>
Date:   Mon, 6 Jul 2020 12:48:05 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Petr Machata <petrm@...lanox.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Ido Schimmel <idosch@...lanox.com>
Subject: Re: [PATCH net-next v1 2/5] net: sched: Introduce helpers for qevent blocks

On Fri, Jun 26, 2020 at 3:46 PM Petr Machata <petrm@...lanox.com> 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.