netdev - Re: [PATCH net 1/1] net/smc: coordinate wait queues for nonblocking connect

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Date:   Wed, 20 Jun 2018 15:56:27 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Ursula Braun <ubraun@...ux.ibm.com>
Cc:     David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        linux-s390@...r.kernel.org, schwidefsky@...ibm.com,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        raspl@...ux.ibm.com, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH net 1/1] net/smc: coordinate wait queues for nonblocking connect

On Wed, Jun 20, 2018 at 1:07 AM, Ursula Braun <ubraun@...ux.ibm.com> wrote:
> diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
> index da7f02edcd37..21c84b924ffb 100644
> --- a/net/smc/af_smc.c
> +++ b/net/smc/af_smc.c
> @@ -605,6 +605,8 @@ static int smc_connect(struct socket *sock, struct sockaddr *addr,
>
>         smc_copy_sock_settings_to_clc(smc);
>         tcp_sk(smc->clcsock->sk)->syn_smc = 1;
> +       if (flags & O_NONBLOCK)
> +               sock->sk->sk_wq = smc->clcsock->sk->sk_wq;
>         rc = kernel_connect(smc->clcsock, addr, alen, flags);
>         if (rc)
>                 goto out;
> @@ -1285,12 +1287,9 @@ static __poll_t smc_poll_mask(struct socket *sock, __poll_t events)
>
>         smc = smc_sk(sock->sk);
>         sock_hold(sk);
> -       lock_sock(sk);
>         if ((sk->sk_state == SMC_INIT) || smc->use_fallback) {
>                 /* delegate to CLC child sock */
> -               release_sock(sk);
>                 mask = smc->clcsock->ops->poll_mask(smc->clcsock, events);
> -               lock_sock(sk);
>                 sk->sk_err = smc->clcsock->sk->sk_err;
>                 if (sk->sk_err) {
>                         mask |= EPOLLERR;
> @@ -1299,7 +1298,10 @@ static __poll_t smc_poll_mask(struct socket *sock, __poll_t events)
>                         if (sk->sk_state == SMC_INIT &&
>                             mask & EPOLLOUT &&
>                             smc->clcsock->sk->sk_state != TCP_CLOSE) {
> +                               sock->sk->sk_wq = smc->smcwq;
> +                               lock_sock(sk);

I think you need to use proper RCU API to protect these
assignment of sk->sk_wq.