linux-kernel - Re: [PATCH v4] net: use exponential backoff in netdev_wait

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Message-ID: <CANn89iKOAfFzj0oJiN99_2hUqnB=vu-rYjd_sAxQYucS28wKMQ@mail.gmail.com>
Date:   Fri, 18 Sep 2020 22:26:15 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Francesco Ruggeri <fruggeri@...sta.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Taehee Yoo <ap420073@...il.com>,
        Andrii Nakryiko <andriin@...com>,
        Jiri Pirko <jiri@...lanox.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH v4] net: use exponential backoff in netdev_wait_allrefs

On Fri, Sep 18, 2020 at 10:19 PM Francesco Ruggeri <fruggeri@...sta.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@...sta.com>
>

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

Thanks !