linux-kernel - Re: A potential deadlock in sockhash map

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Message-ID: <ZA4owxvldelZ6x9h@pop-os.localdomain>
Date:   Sun, 12 Mar 2023 12:32:19 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Hsin-Wei Hung <hsinweih@....edu>
Cc:     John Fastabend <john.fastabend@...il.com>,
        Jakub Sitnicki <jakub@...udflare.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: A potential deadlock in sockhash map

On Mon, Feb 20, 2023 at 07:39:59AM -0600, Hsin-Wei Hung wrote:
> DEFINE_BPF_MAP(map_0, BPF_MAP_TYPE_SOCKHASH, 0, uint32_t, uint32_t, 1005);
> SEC("tp/sched/sched_switch")
> int func(__u64 *ctx) {
>         uint32_t v0 = 0;
>         uint64_t v1 = 0;
>         v1 = bpf_map_delete_elem(&map_0, &v0);
>         return 0;
> }

It looks like we have to disable hardirq (instead of just softirq) in order to use
sockmap safely in interrupt context like sched/sched_switch.

Thanks.