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Date:   Fri, 6 May 2022 13:31:11 -0700
From:   Stephen Hemminger <stephen@networkplumber.org>
To:     Peilin Ye <yepeilin.cs@gmail.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <eric.dumazet@gmail.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        Jiri Pirko <jiri@resnulli.us>,
        Peilin Ye <peilin.ye@bytedance.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, Cong Wang <cong.wang@bytedance.com>
Subject: Re: [PATCH RFC v1 net-next 1/4] net: Introduce Qdisc backpressure
 infrastructure
Message-ID: <20220506133111.1d4bebf3@hermes.local>
In-Reply-To: <f4090d129b685df72070f708294550fbc513f888.1651800598.git.peilin.ye@bytedance.com>
References: <cover.1651800598.git.peilin.ye@bytedance.com>
        <f4090d129b685df72070f708294550fbc513f888.1651800598.git.peilin.ye@bytedance.com>
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On Fri,  6 May 2022 12:44:22 -0700
Peilin Ye <yepeilin.cs@gmail.com> wrote:

> +static inline void qdisc_backpressure_overlimit(struct Qdisc *sch, struct sk_buff *skb)
> +{
> +	struct sock *sk = skb->sk;
> +
> +	if (!sk || !sk_fullsock(sk))
> +		return;
> +
> +	if (cmpxchg(&sk->sk_backpressure_status, SK_UNTHROTTLED, SK_OVERLIMIT) == SK_UNTHROTTLED) {
> +		sock_hold(sk);
> +		list_add_tail(&sk->sk_backpressure_node, &sch->backpressure_list);
> +	}
> +}

What if socket is closed? You are holding reference but application maybe gone.

Or if output is stalled indefinitely?