Convert the ARP packet hold queue from mbuf list to mbuf queue which

contins a mutex.  Update la_hold_total with atomic operations.
OK sashan@

diff --git a/sys/netinet/if_ether.c b/sys/netinet/if_ether.c
index 79ea9e1..bdc5d5f 100644 (file)
--- a/sys/netinet/if_ether.c
+++ b/sys/netinet/if_ether.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: if_ether.c,v 1.245 2021/04/23 21:55:36 bluhm Exp $    */
+/*     $OpenBSD: if_ether.c,v 1.246 2021/04/26 07:55:16 bluhm Exp $    */
 /*     $NetBSD: if_ether.c,v 1.31 1996/05/11 12:59:58 mycroft Exp $    */
 
 /*
@@ -68,7 +68,7 @@
 struct llinfo_arp {
        LIST_ENTRY(llinfo_arp)   la_list;
        struct rtentry          *la_rt;         /* backpointer to rtentry */
-       struct mbuf_list         la_ml;         /* packet hold queue */
+       struct mbuf_queue        la_mq;         /* packet hold queue */
        time_t                   la_refreshed;  /* when was refresh sent */
        int                      la_asked;      /* number of queries sent */
 };
@@ -189,7 +189,7 @@ arp_rtrequest(struct ifnet *ifp, int req, struct rtentry *rt)
                        break;
                }
 
-               ml_init(&la->la_ml);
+               mq_init(&la->la_mq, LA_HOLD_QUEUE, IPL_SOFTNET);
                la->la_rt = rt;
                rt->rt_flags |= RTF_LLINFO;
                if ((rt->rt_flags & RTF_LOCAL) == 0)
@@ -203,7 +203,7 @@ arp_rtrequest(struct ifnet *ifp, int req, struct rtentry *rt)
                LIST_REMOVE(la, la_list);
                rt->rt_llinfo = NULL;
                rt->rt_flags &= ~RTF_LLINFO;
-               la_hold_total -= ml_purge(&la->la_ml);
+               atomic_sub_int(&la_hold_total, mq_purge(&la->la_mq));
                pool_put(&arp_pool, la);
                break;
 
@@ -374,18 +374,11 @@ arpresolve(struct ifnet *ifp, struct rtentry *rt0, struct mbuf *m,
         * response yet. Insert mbuf in hold queue if below limit
         * if above the limit free the queue without queuing the new packet.
         */
-       if (la_hold_total < LA_HOLD_TOTAL) {
-               struct mbuf *mh;
-
-               if (ml_len(&la->la_ml) >= LA_HOLD_QUEUE) {
-                       mh = ml_dequeue(&la->la_ml);
-                       la_hold_total--;
-                       m_freem(mh);
-               }
-               ml_enqueue(&la->la_ml, m);
-               la_hold_total++;
+       if (atomic_inc_int_nv(&la_hold_total) <= LA_HOLD_TOTAL) {
+               if (mq_push(&la->la_mq, m) != 0)
+                       atomic_dec_int(&la_hold_total);
        } else {
-               la_hold_total -= ml_purge(&la->la_ml);
+               atomic_sub_int(&la_hold_total, mq_purge(&la->la_mq) + 1);
                m_freem(m);
        }
 
@@ -414,7 +407,8 @@ arpresolve(struct ifnet *ifp, struct rtentry *rt0, struct mbuf *m,
                                rt->rt_expire += arpt_down;
                                la->la_asked = 0;
                                la->la_refreshed = 0;
-                               la_hold_total -= ml_purge(&la->la_ml);
+                               atomic_sub_int(&la_hold_total,
+                                   mq_purge(&la->la_mq));
                        }
                }
        }
@@ -600,7 +594,7 @@ arpcache(struct ifnet *ifp, struct ether_arp *ea, struct rtentry *rt)
        struct in_addr *spa = (struct in_addr *)ea->arp_spa;
        char addr[INET_ADDRSTRLEN];
        struct ifnet *rifp;
-       unsigned int len;
+       struct mbuf *m;
        int changed = 0;
 
        KERNEL_ASSERT_LOCKED();
@@ -672,20 +666,18 @@ arpcache(struct ifnet *ifp, struct ether_arp *ea, struct rtentry *rt)
 
        la->la_asked = 0;
        la->la_refreshed = 0;
-       while ((len = ml_len(&la->la_ml)) != 0) {
-               struct mbuf *mh;
+       while ((m = mq_dequeue(&la->la_mq)) != NULL) {
+               unsigned int len;
 
-               mh = ml_dequeue(&la->la_ml);
-               la_hold_total--;
+               atomic_dec_int(&la_hold_total);
+               len = mq_len(&la->la_mq);
 
-               ifp->if_output(ifp, mh, rt_key(rt), rt);
+               ifp->if_output(ifp, m, rt_key(rt), rt);
 
-               if (ml_len(&la->la_ml) == len) {
+               /* XXXSMP we discard if other CPU enqueues */
+               if (mq_len(&la->la_mq) > len) {
                        /* mbuf is back in queue. Discard. */
-                       while ((mh = ml_dequeue(&la->la_ml)) != NULL) {
-                               la_hold_total--;
-                               m_freem(mh);
-                       }
+                       atomic_sub_int(&la_hold_total, mq_purge(&la->la_mq));
                        break;
                }
        }
@@ -699,7 +691,7 @@ arpinvalidate(struct rtentry *rt)
        struct llinfo_arp *la = (struct llinfo_arp *)rt->rt_llinfo;
        struct sockaddr_dl *sdl = satosdl(rt->rt_gateway);
 
-       la_hold_total -= ml_purge(&la->la_ml);
+       atomic_sub_int(&la_hold_total, mq_purge(&la->la_mq));
        sdl->sdl_alen = 0;
        la->la_asked = 0;
 }