pkt_sched: remove unnecessary xchg() in packet schedulers
Patrick McHardy [Thu, 20 Nov 2008 12:11:36 +0000 (04:11 -0800)]
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
net/sched/sch_cbq.c
net/sched/sch_drr.c
net/sched/sch_dsmark.c
net/sched/sch_hfsc.c
net/sched/sch_htb.c
net/sched/sch_multiq.c
net/sched/sch_netem.c
net/sched/sch_prio.c
net/sched/sch_red.c
net/sched/sch_tbf.c

index ca90f6e..2a8b83a 100644 (file)
@@ -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;
index a99e37e..3a9569a 100644 (file)
@@ -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])
index e71a5de..8d523d9 100644 (file)
@@ -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;
 }
index 3f9427a..d303daa 100644 (file)
@@ -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);
index 071c474..51dd3f4 100644 (file)
@@ -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;
 }
index 83f5e69..3a119f5 100644 (file)
@@ -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);
                }
index f645ac5..7e15186 100644 (file)
@@ -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);
                        }
index 3cbc3ff..f840d6b 100644 (file)
@@ -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;
 }
 
index ea65a87..94cecef 100644 (file)
@@ -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);
                        }
index 6a0371c..2bdf241 100644 (file)
@@ -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);
index bb7783d..a2f93c0 100644 (file)
@@ -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);