From: Cong Wang <xiyou.wangcong@gmail.com>
To: Yunsheng Lin <linyunsheng@huawei.com>
Cc: David Miller <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Vladimir Oltean <olteanv@gmail.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andriin@fb.com>,
Eric Dumazet <edumazet@google.com>, Wei Wang <weiwan@google.com>,
"Cong Wang ." <cong.wang@bytedance.com>,
Taehee Yoo <ap420073@gmail.com>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
linuxarm@openeuler.org, Marc Kleine-Budde <mkl@pengutronix.de>,
linux-can@vger.kernel.org, Jamal Hadi Salim <jhs@mojatatu.com>,
Jiri Pirko <jiri@resnulli.us>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
kpsingh@kernel.org, bpf <bpf@vger.kernel.org>,
Jonas Bonn <jonas.bonn@netrounds.com>,
Paolo Abeni <pabeni@redhat.com>,
Michael Zhivich <mzhivich@akamai.com>,
Josh Hunt <johunt@akamai.com>, Jike Song <albcamus@gmail.com>,
Kehuan Feng <kehuan.feng@gmail.com>,
Ahmad Fatoum <a.fatoum@pengutronix.de>,
atenart@kernel.org, Alexander Duyck <alexander.duyck@gmail.com>
Subject: Re: [PATCH net v2] net: sched: fix packet stuck problem for lockless qdisc
Date: Wed, 24 Mar 2021 12:20:27 -0700 [thread overview]
Message-ID: <CAM_iQpXAedg31hPx674u4Q4fj0DweADPSn0n_KghgRBWDoOOfw@mail.gmail.com> (raw)
In-Reply-To: <1616552677-39016-1-git-send-email-linyunsheng@huawei.com>
On Tue, Mar 23, 2021 at 7:24 PM Yunsheng Lin <linyunsheng@huawei.com> wrote:
> @@ -176,8 +207,23 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc)
> static inline void qdisc_run_end(struct Qdisc *qdisc)
> {
> write_seqcount_end(&qdisc->running);
> - if (qdisc->flags & TCQ_F_NOLOCK)
> + if (qdisc->flags & TCQ_F_NOLOCK) {
> spin_unlock(&qdisc->seqlock);
> +
> + /* qdisc_run_end() is protected by RCU lock, and
> + * qdisc reset will do a synchronize_net() after
> + * setting __QDISC_STATE_DEACTIVATED, so testing
> + * the below two bits separately should be fine.
Hmm, why synchronize_net() after setting this bit is fine? It could
still be flipped right after you test RESCHEDULE bit.
> + * For qdisc_run() in net_tx_action() case, we
> + * really should provide rcu protection explicitly
> + * for document purposes or PREEMPT_RCU.
> + */
> + if (unlikely(test_bit(__QDISC_STATE_NEED_RESCHEDULE,
> + &qdisc->state) &&
> + !test_bit(__QDISC_STATE_DEACTIVATED,
> + &qdisc->state)))
Why do you want to test __QDISC_STATE_DEACTIVATED bit at all?
dev_deactivate_many() will wait for those scheduled but being
deactivated, so what's the problem of scheduling it even with this bit?
Thanks.
next prev parent reply other threads:[~2021-03-24 19:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-24 2:24 [PATCH net v2] net: sched: fix packet stuck problem for lockless qdisc Yunsheng Lin
2021-03-24 19:20 ` Cong Wang [this message]
2021-03-25 2:08 ` Yunsheng Lin
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