simplify ifq_deq_rollback by only having it unlock.

hfsc needed a rollback ifqop to requeue the mbuf because it used
ml_dequeue in the begin op. now it uses MBUF_LIST_FIRST to get a
ref to the first mbuf in deq_begin.

now the disciplines dont need a rollback op, so ifq_deq_rollback
can be simplified to just releasing the mutex.

based on a discussion with kenjiro cho

3 files changed, 10 insertions, 33 deletions

diff --git a/sys/net/hfsc.c b/sys/net/hfsc.c
index 05cd4f9e978..969138b33b5 100644
--- a/sys/net/hfsc.c
+++ b/sys/net/hfsc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: hfsc.c,v 1.31 2015/11/20 03:35:23 dlg Exp $	*/
+/*	$OpenBSD: hfsc.c,v 1.32 2015/11/21 01:08:49 dlg Exp $	*/
 
 /*
  * Copyright (c) 2012-2013 Henning Brauer <henning@openbsd.org>
@@ -264,7 +264,6 @@ void		 hfsc_free(void *);
 int		 hfsc_enq(struct ifqueue *, struct mbuf *);
 struct mbuf	*hfsc_deq_begin(struct ifqueue *, void **);
 void		 hfsc_deq_commit(struct ifqueue *, struct mbuf *, void *);
-void		 hfsc_deq_rollback(struct ifqueue *, struct mbuf *, void *);
 void		 hfsc_purge(struct ifqueue *, struct mbuf_list *);
 
 const struct ifq_ops hfsc_ops = {
@@ -273,7 +272,6 @@ const struct ifq_ops hfsc_ops = {
         hfsc_enq,
         hfsc_deq_begin,
         hfsc_deq_commit,
-        hfsc_deq_rollback,
         hfsc_purge,
 };
 
@@ -711,7 +709,7 @@ hfsc_deq_begin(struct ifqueue *ifq, void **cookiep)
 			return (NULL);
 	}
 
-	m = ml_dequeue(&cl->cl_q.q);
+	m = MBUF_LIST_FIRST(&cl->cl_q.q);
 	KASSERT(m != NULL);
 
 	hif->hif_microtime = cur_time;
@@ -724,6 +722,7 @@ hfsc_deq_commit(struct ifqueue *ifq, struct mbuf *m, void *cookie)
 {
 	struct hfsc_if *hif = ifq->ifq_q;
 	struct hfsc_class *cl = cookie;
+	struct mbuf *m0;
 	int next_len, realtime = 0;
 	u_int64_t cur_time = hif->hif_microtime;
 
@@ -731,6 +730,9 @@ hfsc_deq_commit(struct ifqueue *ifq, struct mbuf *m, void *cookie)
 	if (cl->cl_rsc != NULL)
 		realtime = (cl->cl_e <= cur_time);
 
+	m0 = ml_dequeue(&cl->cl_q.q);
+	KASSERT(m == m0);
+
 	PKTCNTR_INC(&cl->cl_stats.xmit_cnt, m->m_pkthdr.len);
 
 	hfsc_update_vf(cl, m->m_pkthdr.len, cur_time);
@@ -740,7 +742,8 @@ hfsc_deq_commit(struct ifqueue *ifq, struct mbuf *m, void *cookie)
 	if (ml_len(&cl->cl_q.q) > 0) {
 		if (cl->cl_rsc != NULL) {
 			/* update ed */
-			next_len = cl->cl_q.q.ml_head->m_pkthdr.len;
+			m0 = MBUF_LIST_FIRST(&cl->cl_q.q);
+			next_len = m0->m_pkthdr.len;
 
 			if (realtime)
 				hfsc_update_ed(hif, cl, next_len);
@@ -754,14 +757,6 @@ hfsc_deq_commit(struct ifqueue *ifq, struct mbuf *m, void *cookie)
 }
 
 void
-hfsc_deq_rollback(struct ifqueue *ifq, struct mbuf *m, void *cookie)
-{
-	struct hfsc_class *cl = cookie;
-
-	ml_requeue(&cl->cl_q.q, m);
-}
-
-void
 hfsc_deferred(void *arg)
 {
 	struct ifnet *ifp = arg;
diff --git a/sys/net/if.c b/sys/net/if.c
index 47532fbbf15..e54741aaa43 100644
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if.c,v 1.411 2015/11/20 12:27:42 mpi Exp $	*/
+/*	$OpenBSD: if.c,v 1.412 2015/11/21 01:08:49 dlg Exp $	*/
 /*	$NetBSD: if.c,v 1.35 1996/05/07 05:26:04 thorpej Exp $	*/
 
 /*
@@ -2734,7 +2734,6 @@ void		 priq_free(void *);
 int		 priq_enq(struct ifqueue *, struct mbuf *);
 struct mbuf	*priq_deq_begin(struct ifqueue *, void **);
 void		 priq_deq_commit(struct ifqueue *, struct mbuf *, void *);
-void		 priq_deq_rollback(struct ifqueue *, struct mbuf *, void *);
 void		 priq_purge(struct ifqueue *, struct mbuf_list *);
 
 const struct ifq_ops priq_ops = {
@@ -2743,7 +2742,6 @@ const struct ifq_ops priq_ops = {
 	priq_enq,
 	priq_deq_begin,
 	priq_deq_commit,
-	priq_deq_rollback,
 	priq_purge,
 };
 
@@ -2828,16 +2826,6 @@ priq_deq_commit(struct ifqueue *ifq, struct mbuf *m, void *cookie)
 }
 
 void
-priq_deq_rollback(struct ifqueue *ifq, struct mbuf *m, void *cookie)
-{
-#ifdef DIAGNOSTIC
-	struct priq_list *pl = cookie;
-
-	KASSERT(pl->head == m);
-#endif
-}
-
-void
 priq_purge(struct ifqueue *ifq, struct mbuf_list *ml)
 {
 	struct priq *pq = ifq->ifq_q;
@@ -2919,12 +2907,8 @@ ifq_deq_commit(struct ifqueue *ifq, struct mbuf *m)
 void
 ifq_deq_rollback(struct ifqueue *ifq, struct mbuf *m)
 {
-	void *cookie;
-
 	KASSERT(m != NULL);
-	cookie = m->m_pkthdr.ph_cookie;
 
-	ifq->ifq_ops->ifqop_deq_rollback(ifq, m, cookie);
 	mtx_leave(&ifq->ifq_mtx);
 }
 
diff --git a/sys/net/if_var.h b/sys/net/if_var.h
index 2739ac8a9a5..4c17520ae41 100644
--- a/sys/net/if_var.h
+++ b/sys/net/if_var.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_var.h,v 1.55 2015/11/20 11:15:07 dlg Exp $	*/
+/*	$OpenBSD: if_var.h,v 1.56 2015/11/21 01:08:50 dlg Exp $	*/
 /*	$NetBSD: if.h,v 1.23 1996/05/07 02:40:27 thorpej Exp $	*/
 
 /*
@@ -110,8 +110,6 @@ struct ifq_ops {
 	struct mbuf 		*(*ifqop_deq_begin)(struct ifqueue *, void **);
 	void			 (*ifqop_deq_commit)(struct ifqueue *,
 				    struct mbuf *, void *);
-	void			 (*ifqop_deq_rollback)(struct ifqueue *,
-				    struct mbuf *, void *);
 	void	 		 (*ifqop_purge)(struct ifqueue *,
 				    struct mbuf_list *);
 };