netdev - Re: net/dccp: warning in dccp_feat_clone_sp_val/__might

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Date:   Mon, 31 Oct 2016 11:40:16 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Gerrit Renker <gerrit@....abdn.ac.uk>,
        "David S. Miller" <davem@...emloft.net>, dccp@...r.kernel.org,
        netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: net/dccp: warning in dccp_feat_clone_sp_val/__might_sleep

On Mon, 2016-10-31 at 11:00 -0700, Cong Wang wrote:
> On Sun, Oct 30, 2016 at 6:20 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > On Sun, 2016-10-30 at 05:41 +0100, Andrey Konovalov wrote:
> >> Sorry, the warning is still there.
> >>
> >> I'm not sure adding sched_annotate_sleep() does anything, since it's
> >> defined as (in case CONFIG_DEBUG_ATOMIC_SLEEP is not set):
> >> # define sched_annotate_sleep() do { } while (0)
> >
> > Thanks again for testing.
> >
> > But you do have CONFIG_DEBUG_ATOMIC_SLEEP set, which triggers a check in
> > __might_sleep() :
> >
> > WARN_ONCE(current->state != TASK_RUNNING && current->task_state_change,
> >
> > Relevant commit is 00845eb968ead28007338b2bb852b8beef816583
> > ("sched: don't cause task state changes in nested sleep debugging")
> >
> > Another relevant commit was 26cabd31259ba43f68026ce3f62b78094124333f
> > ("sched, net: Clean up sk_wait_event() vs. might_sleep()")
> >
> > Before release_sock() could process the backlog in process context, only
> > lock_sock() could trigger the issue, so my fix at that time was commit
> > cb7cf8a33ff73cf638481d1edf883d8968f934f8 ("inet: Clean up
> > inet_csk_wait_for_connect() vs. might_sleep()")
> >
> 
> Thanks for the context, but isn't the original warning reported by Andrey is
> from inet_wait_for_connect()? You seem only patch some dccp function
> which is why it is still there?
> 
> It should be the following, no?
> 
> 
> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> index 9648c97..bbd8159 100644
> --- a/net/ipv4/af_inet.c
> +++ b/net/ipv4/af_inet.c
> @@ -544,6 +544,7 @@ static long inet_wait_for_connect(struct sock *sk,
> long timeo, int writebias)
>          * without closing the socket.
>          */
>         while ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
> +               sched_annotate_sleep();
>                 release_sock(sk);
>                 timeo = schedule_timeout(timeo);
>                 lock_sock(sk);

Yes, this would be one of the locations needing this.