netdev - Re: -Wsometimes-uninitialized Clang warning in net/tipc/node.c

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Date:   Thu, 21 Mar 2019 19:22:46 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Jon Maloy <jon.maloy@...csson.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Ying Xue <ying.xue@...driver.com>,
        "David S. Miller" <davem@...emloft.net>,
        "tipc-discussion@...ts.sourceforge.net" 
        <tipc-discussion@...ts.sourceforge.net>,
        Networking <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "clang-built-linux@...glegroups.com" 
        <clang-built-linux@...glegroups.com>
Subject: Re: -Wsometimes-uninitialized Clang warning in net/tipc/node.c

On Thu, Mar 21, 2019 at 4:25 PM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Thu, Mar 21, 2019 at 3:57 PM Jon Maloy <jon.maloy@...csson.com> wrote:

> > >
> > > diff --git a/net/tipc/node.c b/net/tipc/node.c index
> > > 2dc4919ab23c..147786795e48 100644
> > > --- a/net/tipc/node.c
> > > +++ b/net/tipc/node.c
> > > @@ -844,7 +844,8 @@ static void tipc_node_link_down(struct tipc_node *n,
> > > int bearer_id, bool delete)
> > >         tipc_node_write_unlock(n);
> > >         if (delete)
> > >                 tipc_mon_remove_peer(n->net, n->addr, old_bearer_id);
> > > -       tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
> > > +       if (skb_queue_empty(xmitq))
> > > +               tipc_bearer_xmit(n->net, bearer_id, &xmitq, maddr);
> > >         tipc_sk_rcv(n->net, &le->inputq);  }
> > >
> > > This duplicates the check inside of skb_queue_empty(), but I don't know if
> > > the compiler can see through the logic behind the inlined function calls.
> >
> > Probably not, but this is not in any way time critical.
>
> I meant it's unclear whether compilers should be expected to see that
> skb_queue_empty() is true after the call to __skb_queue_head_init()
> initializes it.

I reproduced the warning now, and verified that my change
eliminates the warning. I still think that is the more logical
solution here.

      Arnd