svn commit: r356240 - head/sys/netinet

[Alexander Motin]

Hi,

We hit it on 11.3. So I am going to MFC it.

On Tue, Dec 31, 2019, 9:37 PM Kubilay Kocak <koobs at freebsd.org> wrote:

> On 1/01/2020 5:58 am, Alexander Motin wrote:
> > Author: mav
> > Date: Tue Dec 31 18:58:29 2019
> > New Revision: 356240
> > URL: https://svnweb.freebsd.org/changeset/base/356240
> >
> > Log:
> >    Relax locking of carp_forus().
> >
> >    This fixes deadlock between CARP and bridge.  Bridge calls this
> function
> >    taking CARP lock while holding bridge lock.  Same time CARP tries to
> send
> >    its announcements via the bridge while holding CARP lock.
> >
> >    Use of CARP_LOCK() here does not solve anything, since sc_addr is
> constant
> >    while race on sc_state is harmless and use of the lock does not close
> it.
> >
> >    Reviewed by:       glebius
> >    MFC after: 2 weeks
> >    Sponsored by:      iXsystems, Inc.
> >
> > Modified:
> >    head/sys/netinet/ip_carp.c
> >
> > Modified: head/sys/netinet/ip_carp.c
> >
> ==============================================================================
> > --- head/sys/netinet/ip_carp.c        Tue Dec 31 18:28:25 2019
> (r356239)
> > +++ head/sys/netinet/ip_carp.c        Tue Dec 31 18:58:29 2019
> (r356240)
> > @@ -1230,14 +1230,15 @@ carp_forus(struct ifnet *ifp, u_char *dhost)
> >
> >       CIF_LOCK(ifp->if_carp);
> >       IFNET_FOREACH_CARP(ifp, sc) {
> > -             CARP_LOCK(sc);
> > +             /*
> > +              * CARP_LOCK() is not here, since would protect nothing,
> but
> > +              * cause deadlock with if_bridge, calling this under its
> lock.
> > +              */
> >               if (sc->sc_state == MASTER && !bcmp(dhost,
> LLADDR(&sc->sc_addr),
> >                   ETHER_ADDR_LEN)) {
> > -                     CARP_UNLOCK(sc);
> >                       CIF_UNLOCK(ifp->if_carp);
> >                       return (1);
> >               }
> > -             CARP_UNLOCK(sc);
> >       }
> >       CIF_UNLOCK(ifp->if_carp);
> >
> > _______________________________________________
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> >
>
> Hi Alexander,
>
> Is this a only-head-impacted fix, or does the issue impact stable/12,11
> too, warranting MFC ?
>