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pkt_sched: Add and use qdisc_root() and qdisc_root_lock().
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When code wants to lock the qdisc tree state, the logic
operation it's doing is locking the top-level qdisc that
sits of the root of the netdev_queue.

Add qdisc_root_lock() to represent this and convert the
easiest cases.

In order for this to work out in all cases, we have to
hook up the noop_qdisc to a dummy netdev_queue.

Signed-off-by: David S. Miller <davem@davemloft.net>
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David S. Miller committed Jul 18, 2008
1 parent e2627c8 commit 7698b4f
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Showing 7 changed files with 55 additions and 26 deletions.
12 changes: 12 additions & 0 deletions include/net/sch_generic.h
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Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,18 @@ struct tcf_proto
struct tcf_proto_ops *ops;
};

static inline struct Qdisc *qdisc_root(struct Qdisc *qdisc)
{
return qdisc->dev_queue->qdisc;
}

static inline spinlock_t *qdisc_root_lock(struct Qdisc *qdisc)
{
struct Qdisc *root = qdisc_root(qdisc);

return &root->dev_queue->lock;
}

static inline struct net_device *qdisc_dev(struct Qdisc *qdisc)
{
return qdisc->dev_queue->dev;
Expand Down
8 changes: 4 additions & 4 deletions net/sched/sch_api.c
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Original file line number Diff line number Diff line change
Expand Up @@ -633,7 +633,7 @@ qdisc_create(struct net_device *dev, struct netdev_queue *dev_queue,
if (!ops->init || (err = ops->init(sch, tca[TCA_OPTIONS])) == 0) {
if (tca[TCA_RATE]) {
err = gen_new_estimator(&sch->bstats, &sch->rate_est,
&sch->dev_queue->lock,
qdisc_root_lock(sch),
tca[TCA_RATE]);
if (err) {
/*
Expand Down Expand Up @@ -675,7 +675,7 @@ static int qdisc_change(struct Qdisc *sch, struct nlattr **tca)
}
if (tca[TCA_RATE])
gen_replace_estimator(&sch->bstats, &sch->rate_est,
&sch->dev_queue->lock, tca[TCA_RATE]);
qdisc_root_lock(sch), tca[TCA_RATE]);
return 0;
}

Expand Down Expand Up @@ -967,7 +967,7 @@ static int tc_fill_qdisc(struct sk_buff *skb, struct Qdisc *q, u32 clid,
q->qstats.qlen = q->q.qlen;

if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS,
TCA_XSTATS, &q->dev_queue->lock, &d) < 0)
TCA_XSTATS, qdisc_root_lock(q), &d) < 0)
goto nla_put_failure;

if (q->ops->dump_stats && q->ops->dump_stats(q, &d) < 0)
Expand Down Expand Up @@ -1216,7 +1216,7 @@ static int tc_fill_tclass(struct sk_buff *skb, struct Qdisc *q,
goto nla_put_failure;

if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS,
TCA_XSTATS, &q->dev_queue->lock, &d) < 0)
TCA_XSTATS, qdisc_root_lock(q), &d) < 0)
goto nla_put_failure;

if (cl_ops->dump_stats && cl_ops->dump_stats(q, cl, &d) < 0)
Expand Down
9 changes: 5 additions & 4 deletions net/sched/sch_cbq.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1744,12 +1744,13 @@ static void cbq_put(struct Qdisc *sch, unsigned long arg)

if (--cl->refcnt == 0) {
#ifdef CONFIG_NET_CLS_ACT
spinlock_t *root_lock = qdisc_root_lock(sch);
struct cbq_sched_data *q = qdisc_priv(sch);

spin_lock_bh(&sch->dev_queue->lock);
spin_lock_bh(root_lock);
if (q->rx_class == cl)
q->rx_class = NULL;
spin_unlock_bh(&sch->dev_queue->lock);
spin_unlock_bh(root_lock);
#endif

cbq_destroy_class(sch, cl);
Expand Down Expand Up @@ -1828,7 +1829,7 @@ cbq_change_class(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **t

if (tca[TCA_RATE])
gen_replace_estimator(&cl->bstats, &cl->rate_est,
&sch->dev_queue->lock,
qdisc_root_lock(sch),
tca[TCA_RATE]);
return 0;
}
Expand Down Expand Up @@ -1919,7 +1920,7 @@ cbq_change_class(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **t

if (tca[TCA_RATE])
gen_new_estimator(&cl->bstats, &cl->rate_est,
&sch->dev_queue->lock, tca[TCA_RATE]);
qdisc_root_lock(sch), tca[TCA_RATE]);

*arg = (unsigned long)cl;
return 0;
Expand Down
21 changes: 16 additions & 5 deletions net/sched/sch_generic.c
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Original file line number Diff line number Diff line change
Expand Up @@ -151,14 +151,17 @@ static inline int qdisc_restart(struct netdev_queue *txq,
{
int ret = NETDEV_TX_BUSY;
struct net_device *dev;
spinlock_t *root_lock;
struct sk_buff *skb;

/* Dequeue packet */
if (unlikely((skb = dequeue_skb(q)) == NULL))
return 0;

/* And release queue */
spin_unlock(&txq->lock);
root_lock = qdisc_root_lock(q);

/* And release qdisc */
spin_unlock(root_lock);

dev = txq->dev;

Expand All @@ -167,7 +170,7 @@ static inline int qdisc_restart(struct netdev_queue *txq,
ret = dev_hard_start_xmit(skb, dev, txq);
HARD_TX_UNLOCK(dev, txq);

spin_lock(&txq->lock);
spin_lock(root_lock);

switch (ret) {
case NETDEV_TX_OK:
Expand Down Expand Up @@ -345,12 +348,18 @@ struct Qdisc_ops noop_qdisc_ops __read_mostly = {
.owner = THIS_MODULE,
};

static struct netdev_queue noop_netdev_queue = {
.lock = __SPIN_LOCK_UNLOCKED(noop_netdev_queue.lock),
.qdisc = &noop_qdisc,
};

struct Qdisc noop_qdisc = {
.enqueue = noop_enqueue,
.dequeue = noop_dequeue,
.flags = TCQ_F_BUILTIN,
.ops = &noop_qdisc_ops,
.list = LIST_HEAD_INIT(noop_qdisc.list),
.dev_queue = &noop_netdev_queue,
};
EXPORT_SYMBOL(noop_qdisc);

Expand Down Expand Up @@ -666,19 +675,21 @@ static bool some_qdisc_is_running(struct net_device *dev, int lock)

for (i = 0; i < dev->num_tx_queues; i++) {
struct netdev_queue *dev_queue;
spinlock_t *root_lock;
struct Qdisc *q;
int val;

dev_queue = netdev_get_tx_queue(dev, i);
q = dev_queue->qdisc;
root_lock = qdisc_root_lock(q);

if (lock)
spin_lock_bh(&dev_queue->lock);
spin_lock_bh(root_lock);

val = test_bit(__QDISC_STATE_RUNNING, &q->state);

if (lock)
spin_unlock_bh(&dev_queue->lock);
spin_unlock_bh(root_lock);

if (val)
return true;
Expand Down
4 changes: 2 additions & 2 deletions net/sched/sch_hfsc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1045,7 +1045,7 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid,

if (tca[TCA_RATE])
gen_replace_estimator(&cl->bstats, &cl->rate_est,
&sch->dev_queue->lock,
qdisc_root_lock(sch),
tca[TCA_RATE]);
return 0;
}
Expand Down Expand Up @@ -1104,7 +1104,7 @@ hfsc_change_class(struct Qdisc *sch, u32 classid, u32 parentid,

if (tca[TCA_RATE])
gen_new_estimator(&cl->bstats, &cl->rate_est,
&sch->dev_queue->lock, tca[TCA_RATE]);
qdisc_root_lock(sch), tca[TCA_RATE]);
*arg = (unsigned long)cl;
return 0;
}
Expand Down
18 changes: 10 additions & 8 deletions net/sched/sch_htb.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1039,11 +1039,12 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt)

static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
{
spinlock_t *root_lock = qdisc_root_lock(sch);
struct htb_sched *q = qdisc_priv(sch);
struct nlattr *nest;
struct tc_htb_glob gopt;

spin_lock_bh(&sch->dev_queue->lock);
spin_lock_bh(root_lock);

gopt.direct_pkts = q->direct_pkts;
gopt.version = HTB_VER;
Expand All @@ -1057,11 +1058,11 @@ static int htb_dump(struct Qdisc *sch, struct sk_buff *skb)
NLA_PUT(skb, TCA_HTB_INIT, sizeof(gopt), &gopt);
nla_nest_end(skb, nest);

spin_unlock_bh(&sch->dev_queue->lock);
spin_unlock_bh(root_lock);
return skb->len;

nla_put_failure:
spin_unlock_bh(&sch->dev_queue->lock);
spin_unlock_bh(root_lock);
nla_nest_cancel(skb, nest);
return -1;
}
Expand All @@ -1070,10 +1071,11 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
struct sk_buff *skb, struct tcmsg *tcm)
{
struct htb_class *cl = (struct htb_class *)arg;
spinlock_t *root_lock = qdisc_root_lock(sch);
struct nlattr *nest;
struct tc_htb_opt opt;

spin_lock_bh(&sch->dev_queue->lock);
spin_lock_bh(root_lock);
tcm->tcm_parent = cl->parent ? cl->parent->common.classid : TC_H_ROOT;
tcm->tcm_handle = cl->common.classid;
if (!cl->level && cl->un.leaf.q)
Expand All @@ -1095,11 +1097,11 @@ static int htb_dump_class(struct Qdisc *sch, unsigned long arg,
NLA_PUT(skb, TCA_HTB_PARMS, sizeof(opt), &opt);

nla_nest_end(skb, nest);
spin_unlock_bh(&sch->dev_queue->lock);
spin_unlock_bh(root_lock);
return skb->len;

nla_put_failure:
spin_unlock_bh(&sch->dev_queue->lock);
spin_unlock_bh(root_lock);
nla_nest_cancel(skb, nest);
return -1;
}
Expand Down Expand Up @@ -1365,7 +1367,7 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
goto failure;

gen_new_estimator(&cl->bstats, &cl->rate_est,
&sch->dev_queue->lock,
qdisc_root_lock(sch),
tca[TCA_RATE] ? : &est.nla);
cl->refcnt = 1;
cl->children = 0;
Expand Down Expand Up @@ -1420,7 +1422,7 @@ static int htb_change_class(struct Qdisc *sch, u32 classid,
} else {
if (tca[TCA_RATE])
gen_replace_estimator(&cl->bstats, &cl->rate_est,
&sch->dev_queue->lock,
qdisc_root_lock(sch),
tca[TCA_RATE]);
sch_tree_lock(sch);
}
Expand Down
9 changes: 6 additions & 3 deletions net/sched/sch_netem.c
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Original file line number Diff line number Diff line change
Expand Up @@ -180,7 +180,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
* skb will be queued.
*/
if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
struct Qdisc *rootq = sch->dev_queue->qdisc;
struct Qdisc *rootq = qdisc_root(sch);
u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
q->duplicate = 0;

Expand Down Expand Up @@ -319,6 +319,7 @@ static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
struct netem_sched_data *q = qdisc_priv(sch);
unsigned long n = nla_len(attr)/sizeof(__s16);
const __s16 *data = nla_data(attr);
spinlock_t *root_lock;
struct disttable *d;
int i;

Expand All @@ -333,9 +334,11 @@ static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
for (i = 0; i < n; i++)
d->table[i] = data[i];

spin_lock_bh(&sch->dev_queue->lock);
root_lock = qdisc_root_lock(sch);

spin_lock_bh(root_lock);
d = xchg(&q->delay_dist, d);
spin_unlock_bh(&sch->dev_queue->lock);
spin_unlock_bh(root_lock);

kfree(d);
return 0;
Expand Down

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