Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20221102211350.625011-1-dima@arista.com> <20221102211350.625011-3-dima@arista.com>
 <CANn89iLbOikuG9+Tna9M0Gr-diF2vFpfMV8MDP8rBuN49+Mwrg@mail.gmail.com>
 <483848f5-8807-fd97-babc-44740db96db4@arista.com> <CANn89i+XyQhh0eNMJWNn6NNLDaMtrzX3sq9Atu-ic7P5uqDODg@mail.gmail.com>
In-Reply-To: <CANn89i+XyQhh0eNMJWNn6NNLDaMtrzX3sq9Atu-ic7P5uqDODg@mail.gmail.com>
From:   Eric Dumazet <edumazet@google.com>
Date:   Wed, 2 Nov 2022 14:53:42 -0700
Message-ID: <CANn89i+UxgHwm9apzBXV-afpcfXfuX2S+6i4vPzF2ec4Dr6X0A@mail.gmail.com>
Subject: Re: [PATCH 2/2] net/tcp: Disable TCP-MD5 static key on
 tcp_md5sig_info destruction
To:     Dmitry Safonov <dima@arista.com>
Cc:     linux-kernel@vger.kernel.org, David Ahern <dsahern@kernel.org>,
        Bob Gilligan <gilligan@arista.com>,
        "David S. Miller" <davem@davemloft.net>,
        Dmitry Safonov <0x7f454c46@gmail.com>,
        Francesco Ruggeri <fruggeri@arista.com>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Salam Noureddine <noureddine@arista.com>,
        netdev@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, Nov 2, 2022 at 2:49 PM Eric Dumazet <edumazet@google.com> wrote:

>
> Are you sure ?
>
> static_branch_inc() is what we want here, it is a nice wrapper around
> the correct internal details,
> and ultimately boils to an atomic_inc(). It is safe for all contexts.
>
> But if/when jump labels get refcount_t one day, we will not have to
> change TCP stack because
> it made some implementation assumptions.

Oh, I think I understand this better now.

Please provide a helper like

static inline void static_key_fast_inc(struct static_key *key)
{
       atomic_inc(&key->enabled);
}

Something like that.