From b94c8afcba3ae6584653b98e315446ea83be6ea5 Mon Sep 17 00:00:00 2001
From: Patrick McHardy <kaber@trash.net>
Date: Thu, 20 Nov 2008 04:11:36 -0800
Subject: [PATCH] pkt_sched: remove unnecessary xchg() in packet schedulers

The use of xchg() hasn't been necessary since 2.2.something when proper
locking was added to packet schedulers.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/sched/sch_atm.c    |  3 ++-
 net/sched/sch_cbq.c    |  7 ++++---
 net/sched/sch_drr.c    |  3 ++-
 net/sched/sch_dsmark.c |  3 ++-
 net/sched/sch_hfsc.c   |  3 ++-
 net/sched/sch_htb.c    |  4 +++-
 net/sched/sch_multiq.c | 16 +++++++++-------
 net/sched/sch_netem.c  |  5 ++---
 net/sched/sch_prio.c   | 16 +++++++++-------
 net/sched/sch_red.c    |  6 ++++--
 net/sched/sch_tbf.c    | 17 +++++++++++++----
 11 files changed, 52 insertions(+), 31 deletions(-)

diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c
index ca90f6e59ae..2a8b83af7c4 100644
--- a/net/sched/sch_atm.c
+++ b/net/sched/sch_atm.c
@@ -102,7 +102,8 @@ static int atm_tc_graft(struct Qdisc *sch, unsigned long arg,
 		return -EINVAL;
 	if (!new)
 		new = &noop_qdisc;
-	*old = xchg(&flow->q, new);
+	*old = flow->q;
+	flow->q = new;
 	if (*old)
 		qdisc_reset(*old);
 	return 0;
diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c
index a99e37e9e6f..3a9569a3396 100644
--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -1635,7 +1635,8 @@ static int cbq_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 #endif
 		}
 		sch_tree_lock(sch);
-		*old = xchg(&cl->q, new);
+		*old = cl->q;
+		cl->q = new;
 		qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 		qdisc_reset(*old);
 		sch_tree_unlock(sch);
@@ -1776,8 +1777,8 @@ cbq_change_class(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **t
 			cbq_deactivate_class(cl);
 
 		if (rtab) {
-			rtab = xchg(&cl->R_tab, rtab);
-			qdisc_put_rtab(rtab);
+			qdisc_put_rtab(cl->R_tab);
+			cl->R_tab = rtab;
 		}
 
 		if (tb[TCA_CBQ_LSSOPT])
diff --git a/net/sched/sch_drr.c b/net/sched/sch_drr.c
index e71a5de23e2..8d523d9b636 100644
--- a/net/sched/sch_drr.c
+++ b/net/sched/sch_drr.c
@@ -208,7 +208,8 @@ static int drr_graft_class(struct Qdisc *sch, unsigned long arg,
 
 	sch_tree_lock(sch);
 	drr_purge_queue(cl);
-	*old = xchg(&cl->qdisc, new);
+	*old = cl->qdisc;
+	cl->qdisc = new;
 	sch_tree_unlock(sch);
 	return 0;
 }
diff --git a/net/sched/sch_dsmark.c b/net/sched/sch_dsmark.c
index 3f9427a4b75..d303daa45d4 100644
--- a/net/sched/sch_dsmark.c
+++ b/net/sched/sch_dsmark.c
@@ -68,7 +68,8 @@ static int dsmark_graft(struct Qdisc *sch, unsigned long arg,
 	}
 
 	sch_tree_lock(sch);
-	*old = xchg(&p->q, new);
+	*old = p->q;
+	p->q = new;
 	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 	qdisc_reset(*old);
 	sch_tree_unlock(sch);
diff --git a/net/sched/sch_hfsc.c b/net/sched/sch_hfsc.c
index 071c4749a12..51dd3f40162 100644
--- a/net/sched/sch_hfsc.c
+++ b/net/sched/sch_hfsc.c
@@ -1202,7 +1202,8 @@ hfsc_graft_class(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 
 	sch_tree_lock(sch);
 	hfsc_purge_queue(sch, cl);
-	*old = xchg(&cl->qdisc, new);
+	*old = cl->qdisc;
+	cl->qdisc = new;
 	sch_tree_unlock(sch);
 	return 0;
 }
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 83f5e69243c..3a119f576bb 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -1100,7 +1100,9 @@ static int htb_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 		    == NULL)
 			return -ENOBUFS;
 		sch_tree_lock(sch);
-		if ((*old = xchg(&cl->un.leaf.q, new)) != NULL) {
+		*old = cl->un.leaf.q;
+		cl->un.leaf.q = new;
+		if (*old != NULL) {
 			qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 			qdisc_reset(*old);
 		}
diff --git a/net/sched/sch_multiq.c b/net/sched/sch_multiq.c
index f645ac55a1a..7e151861794 100644
--- a/net/sched/sch_multiq.c
+++ b/net/sched/sch_multiq.c
@@ -214,7 +214,8 @@ static int multiq_tune(struct Qdisc *sch, struct nlattr *opt)
 	q->bands = qopt->bands;
 	for (i = q->bands; i < q->max_bands; i++) {
 		if (q->queues[i] != &noop_qdisc) {
-			struct Qdisc *child = xchg(&q->queues[i], &noop_qdisc);
+			struct Qdisc *child = q->queues[i];
+			q->queues[i] = &noop_qdisc;
 			qdisc_tree_decrease_qlen(child, child->q.qlen);
 			qdisc_destroy(child);
 		}
@@ -224,7 +225,7 @@ static int multiq_tune(struct Qdisc *sch, struct nlattr *opt)
 
 	for (i = 0; i < q->bands; i++) {
 		if (q->queues[i] == &noop_qdisc) {
-			struct Qdisc *child;
+			struct Qdisc *child, *old;
 			child = qdisc_create_dflt(qdisc_dev(sch),
 						  sch->dev_queue,
 						  &pfifo_qdisc_ops,
@@ -232,12 +233,13 @@ static int multiq_tune(struct Qdisc *sch, struct nlattr *opt)
 							    i + 1));
 			if (child) {
 				sch_tree_lock(sch);
-				child = xchg(&q->queues[i], child);
+				old = q->queues[i];
+				q->queues[i] = child;
 
-				if (child != &noop_qdisc) {
-					qdisc_tree_decrease_qlen(child,
-								 child->q.qlen);
-					qdisc_destroy(child);
+				if (old != &noop_qdisc) {
+					qdisc_tree_decrease_qlen(old,
+								 old->q.qlen);
+					qdisc_destroy(old);
 				}
 				sch_tree_unlock(sch);
 			}
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 3cbc3ff7b5b..f840d6b27c6 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -331,10 +331,9 @@ static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
 	root_lock = qdisc_root_sleeping_lock(sch);
 
 	spin_lock_bh(root_lock);
-	d = xchg(&q->delay_dist, d);
+	kfree(q->delay_dist);
+	q->delay_dist = d;
 	spin_unlock_bh(root_lock);
-
-	kfree(d);
 	return 0;
 }
 
diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
index ea65a87ec22..94cecef7014 100644
--- a/net/sched/sch_prio.c
+++ b/net/sched/sch_prio.c
@@ -187,7 +187,8 @@ static int prio_tune(struct Qdisc *sch, struct nlattr *opt)
 	memcpy(q->prio2band, qopt->priomap, TC_PRIO_MAX+1);
 
 	for (i=q->bands; i<TCQ_PRIO_BANDS; i++) {
-		struct Qdisc *child = xchg(&q->queues[i], &noop_qdisc);
+		struct Qdisc *child = q->queues[i];
+		q->queues[i] = &noop_qdisc;
 		if (child != &noop_qdisc) {
 			qdisc_tree_decrease_qlen(child, child->q.qlen);
 			qdisc_destroy(child);
@@ -197,18 +198,19 @@ static int prio_tune(struct Qdisc *sch, struct nlattr *opt)
 
 	for (i=0; i<q->bands; i++) {
 		if (q->queues[i] == &noop_qdisc) {
-			struct Qdisc *child;
+			struct Qdisc *child, *old;
 			child = qdisc_create_dflt(qdisc_dev(sch), sch->dev_queue,
 						  &pfifo_qdisc_ops,
 						  TC_H_MAKE(sch->handle, i + 1));
 			if (child) {
 				sch_tree_lock(sch);
-				child = xchg(&q->queues[i], child);
+				old = q->queues[i];
+				q->queues[i] = child;
 
-				if (child != &noop_qdisc) {
-					qdisc_tree_decrease_qlen(child,
-								 child->q.qlen);
-					qdisc_destroy(child);
+				if (old != &noop_qdisc) {
+					qdisc_tree_decrease_qlen(old,
+								 old->q.qlen);
+					qdisc_destroy(old);
 				}
 				sch_tree_unlock(sch);
 			}
diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c
index 6a0371c2264..2bdf241f631 100644
--- a/net/sched/sch_red.c
+++ b/net/sched/sch_red.c
@@ -202,7 +202,8 @@ static int red_change(struct Qdisc *sch, struct nlattr *opt)
 	q->limit = ctl->limit;
 	if (child) {
 		qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
-		qdisc_destroy(xchg(&q->qdisc, child));
+		qdisc_destroy(q->qdisc);
+		q->qdisc = child;
 	}
 
 	red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog,
@@ -283,7 +284,8 @@ static int red_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 		new = &noop_qdisc;
 
 	sch_tree_lock(sch);
-	*old = xchg(&q->qdisc, new);
+	*old = q->qdisc;
+	q->qdisc = new;
 	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 	qdisc_reset(*old);
 	sch_tree_unlock(sch);
diff --git a/net/sched/sch_tbf.c b/net/sched/sch_tbf.c
index bb7783d584b..a2f93c09f3c 100644
--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -236,6 +236,7 @@ static int tbf_change(struct Qdisc* sch, struct nlattr *opt)
 	struct tc_tbf_qopt *qopt;
 	struct qdisc_rate_table *rtab = NULL;
 	struct qdisc_rate_table *ptab = NULL;
+	struct qdisc_rate_table *tmp;
 	struct Qdisc *child = NULL;
 	int max_size,n;
 
@@ -284,7 +285,8 @@ static int tbf_change(struct Qdisc* sch, struct nlattr *opt)
 	sch_tree_lock(sch);
 	if (child) {
 		qdisc_tree_decrease_qlen(q->qdisc, q->qdisc->q.qlen);
-		qdisc_destroy(xchg(&q->qdisc, child));
+		qdisc_destroy(q->qdisc);
+		q->qdisc = child;
 	}
 	q->limit = qopt->limit;
 	q->mtu = qopt->mtu;
@@ -292,8 +294,14 @@ static int tbf_change(struct Qdisc* sch, struct nlattr *opt)
 	q->buffer = qopt->buffer;
 	q->tokens = q->buffer;
 	q->ptokens = q->mtu;
-	rtab = xchg(&q->R_tab, rtab);
-	ptab = xchg(&q->P_tab, ptab);
+
+	tmp = q->R_tab;
+	q->R_tab = rtab;
+	rtab = tmp;
+
+	tmp = q->P_tab;
+	q->P_tab = ptab;
+	ptab = tmp;
 	sch_tree_unlock(sch);
 	err = 0;
 done:
@@ -383,7 +391,8 @@ static int tbf_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
 		new = &noop_qdisc;
 
 	sch_tree_lock(sch);
-	*old = xchg(&q->qdisc, new);
+	*old = q->qdisc;
+	q->qdisc = new;
 	qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
 	qdisc_reset(*old);
 	sch_tree_unlock(sch);
-- 
2.41.1