Re: pppac(4) move ifnet out of KERNEL_LOCK()

[Vitaliy Makkoveev]

Another update. 
The whole "while ((m = ifq_dequeue(ifq)) != NULL)" wrapped by netlock as
it was made for pppx(4). This is to exclude per-packet lock/unlock in
output path.


Index: sys/net/if_pppx.c
===================================================================
RCS file: /cvs/src/sys/net/if_pppx.c,v
retrieving revision 1.98
diff -u -p -r1.98 if_pppx.c
--- sys/net/if_pppx.c   28 Jul 2020 09:53:36 -0000      1.98
+++ sys/net/if_pppx.c   8 Aug 2020 13:28:04 -0000
@@ -1058,7 +1058,7 @@ static int        pppac_ioctl(struct ifnet *, u
 
 static int     pppac_output(struct ifnet *, struct mbuf *, struct sockaddr *,
                    struct rtentry *);
-static void    pppac_start(struct ifnet *);
+static void    pppac_qstart(struct ifqueue *);
 
 static inline struct pppac_softc *
 pppac_lookup(dev_t dev)
@@ -1107,13 +1107,11 @@ pppacopen(dev_t dev, int flags, int mode
        ifp->if_hdrlen = sizeof(uint32_t); /* for BPF */;
        ifp->if_mtu = MAXMCLBYTES - sizeof(uint32_t);
        ifp->if_flags = IFF_SIMPLEX | IFF_BROADCAST;
-       ifp->if_xflags = IFXF_CLONED;
+       ifp->if_xflags = IFXF_CLONED | IFXF_MPSAFE;
        ifp->if_rtrequest = p2p_rtrequest; /* XXX */
        ifp->if_output = pppac_output;
-       ifp->if_start = pppac_start;
+       ifp->if_qstart = pppac_qstart;
        ifp->if_ioctl = pppac_ioctl;
-       /* XXXSMP: be sure pppac_start() called under NET_LOCK() */
-       ifq_set_maxlen(&ifp->if_snd, 1);
 
        if_counters_alloc(ifp);
        if_attach(ifp);
@@ -1382,10 +1380,10 @@ pppacclose(dev_t dev, int flags, int mod
        klist_invalidate(&sc->sc_wsel.si_note);
        splx(s);
 
-       pipex_iface_fini(&sc->sc_pipex_iface);
-
        if_detach(ifp);
 
+       pipex_iface_fini(&sc->sc_pipex_iface);
+
        LIST_REMOVE(sc, sc_entry);
        free(sc, M_DEVBUF, sizeof(*sc));
 
@@ -1459,15 +1457,14 @@ drop:
 }
 
 static void
-pppac_start(struct ifnet *ifp)
+pppac_qstart(struct ifqueue *ifq)
 {
+       struct ifnet *ifp = ifq->ifq_if;
        struct pppac_softc *sc = ifp->if_softc;
        struct mbuf *m;
 
-       if (!ISSET(ifp->if_flags, IFF_RUNNING))
-               return;
-
-       while ((m = ifq_dequeue(&ifp->if_snd)) != NULL) {
+       NET_LOCK();
+       while ((m = ifq_dequeue(ifq)) != NULL) {
 #if NBPFILTER > 0
                if (ifp->if_bpf) {
                        bpf_mtap_af(ifp->if_bpf, m->m_pkthdr.ph_family, m,
@@ -1489,9 +1486,9 @@ pppac_start(struct ifnet *ifp)
 
                mq_enqueue(&sc->sc_mq, m); /* qdrop */
        }
+       NET_UNLOCK();
 
        if (!mq_empty(&sc->sc_mq)) {
-               KERNEL_ASSERT_LOCKED();
                wakeup(sc);
                selwakeup(&sc->sc_rsel);
        }