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Date: Tue, 7 Jul 2020 12:48:27 -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.
I read this again, another question here is: why is tcf_qevent_handle()
special here? We call tcf_classify() under root lock in many other places
too, for example htb_enqueue(), which of course includes act_mirred
execution, so why isn't it a problem there?
People added MIRRED_RECURSION_LIMIT for this kinda recursion,
but never released that root lock.
Thanks.
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