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>

11 files changed, 52 insertions, 31 deletions

diff --git a/net/sched/sch_atm.c b/net/sched/sch_atm.c
index ca90f6e59aee..2a8b83af7c47 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 a99e37e9e6f1..3a9569a3396c 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 e71a5de23e23..8d523d9b636c 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 3f9427a4b757..d303daa45d49 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 071c4749a12b..51dd3f401623 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 83f5e69243c1..3a119f576bb3 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 f645ac55a1a1..7e151861794b 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 3cbc3ff7b5bc..f840d6b27c65 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 ea65a87ec22c..94cecef70145 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 6a0371c22643..2bdf241f6315 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 bb7783d584bb..a2f93c09f3cc 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);