Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20200918201902.0931495C0649@us180.sjc.aristanetworks.com>
In-Reply-To: <20200918201902.0931495C0649@us180.sjc.aristanetworks.com>
From:   Eric Dumazet <edumazet@google.com>
Date:   Fri, 18 Sep 2020 22:26:15 +0200
Message-ID: <CANn89iKOAfFzj0oJiN99_2hUqnB=vu-rYjd_sAxQYucS28wKMQ@mail.gmail.com>
Subject: Re: [PATCH v4] net: use exponential backoff in netdev_wait_allrefs
To:     Francesco Ruggeri <fruggeri@arista.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        Taehee Yoo <ap420073@gmail.com>,
        Andrii Nakryiko <andriin@fb.com>,
        Jiri Pirko <jiri@mellanox.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>,
        David Miller <davem@davemloft.net>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Sep 18, 2020 at 10:19 PM Francesco Ruggeri <fruggeri@arista.com> wrote:
>
> The combination of aca_free_rcu, introduced in commit 2384d02520ff
> ("net/ipv6: Add anycast addresses to a global hashtable"), and
> fib6_info_destroy_rcu, introduced in commit 9b0a8da8c4c6 ("net/ipv6:
> respect rcu grace period before freeing fib6_info"), can result in
> an extra rcu grace period being needed when deleting an interface,
> with the result that netdev_wait_allrefs ends up hitting the msleep(250),
> which is considerably longer than the required grace period.
> This can result in long delays when deleting a large number of interfaces,
> and it can be observed with this script:
>
>
>
> Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
>

Reviewed-by: Eric Dumazet <edumazet@google.com>

Thanks !