[PKT_SCHED]: netetm: make qdisc friendly to outer disciplines

Netem currently dumps packets into the queue when timer expires. This
patch makes work by self-clocking (more like TBF).  It fixes a bug
when 0 delay is requested (only doing loss or duplication).

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 67 insertions, 46 deletions

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 31c29deb139d..864b8d353ffa 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -138,38 +138,78 @@ static long tabledist(unsigned long mu, long sigma,
 }
 
 /* Put skb in the private delayed queue. */
-static int delay_skb(struct Qdisc *sch, struct sk_buff *skb)
+static int netem_delay(struct Qdisc *sch, struct sk_buff *skb)
 {
         struct netem_sched_data *q = qdisc_priv(sch);
-        struct netem_skb_cb *cb = (struct netem_skb_cb *)skb->cb;
         psched_tdiff_t td;
         psched_time_t now;
         
         PSCHED_GET_TIME(now);
         td = tabledist(q->latency, q->jitter, &q->delay_cor, q->delay_dist);
-        PSCHED_TADD2(now, td, cb->time_to_send);
         
         /* Always queue at tail to keep packets in order */
         if (likely(q->delayed.qlen < q->limit)) {
+                struct netem_skb_cb *cb = (struct netem_skb_cb *)skb->cb;
+        
+                PSCHED_TADD2(now, td, cb->time_to_send);
+
+                pr_debug("netem_delay: skb=%p now=%llu tosend=%llu\n", skb, 
+                         now, cb->time_to_send);
+        
                 __skb_queue_tail(&q->delayed, skb);
-                if (!timer_pending(&q->timer)) {
-                        q->timer.expires = jiffies + PSCHED_US2JIFFIE(td);
-                        add_timer(&q->timer);
-                }
                 return NET_XMIT_SUCCESS;
         }
 
+        pr_debug("netem_delay: queue over limit %d\n", q->limit);
+        sch->qstats.overlimits++;
         kfree_skb(skb);
         return NET_XMIT_DROP;
 }
 
+/*
+ *  Move a packet that is ready to send from the delay holding
+ *  list to the underlying qdisc.
+ */
+static int netem_run(struct Qdisc *sch)
+{
+        struct netem_sched_data *q = qdisc_priv(sch);
+        struct sk_buff *skb;
+        psched_time_t now;
+
+        PSCHED_GET_TIME(now);
+
+        skb = skb_peek(&q->delayed);
+        if (skb) {
+                const struct netem_skb_cb *cb
+                        = (const struct netem_skb_cb *)skb->cb;
+                long delay 
+                        = PSCHED_US2JIFFIE(PSCHED_TDIFF(cb->time_to_send, now));
+                pr_debug("netem_run: skb=%p delay=%ld\n", skb, delay);
+
+                /* if more time remaining? */
+                if (delay > 0) {
+                        mod_timer(&q->timer, jiffies + delay);
+                        return 1;
+                }
+
+                __skb_unlink(skb, &q->delayed);
+                
+                if (q->qdisc->enqueue(skb, q->qdisc)) {
+                        sch->q.qlen--;
+                        sch->qstats.drops++;
+                } 
+        }
+
+        return 0;
+}
+
 static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
 {
         struct netem_sched_data *q = qdisc_priv(sch);
         struct sk_buff *skb2;
         int ret;
 
-        pr_debug("netem_enqueue skb=%p @%lu\n", skb, jiffies);
+        pr_debug("netem_enqueue skb=%p\n", skb);
 
         /* Random packet drop 0 => none, ~0 => all */
         if (q->loss && q->loss >= get_crandom(&q->loss_cor)) {
@@ -184,7 +224,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
             && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
                 pr_debug("netem_enqueue: dup %p\n", skb2);
 
-                if (delay_skb(sch, skb2)) {
+                if (netem_delay(sch, skb2)) {
                         sch->q.qlen++;
                         sch->bstats.bytes += skb2->len;
                         sch->bstats.packets++;
@@ -202,7 +242,8 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
                 ret = q->qdisc->enqueue(skb, q->qdisc);
         } else {
                 q->counter = 0;
-                ret = delay_skb(sch, skb);
+                ret = netem_delay(sch, skb);
+                netem_run(sch);
         }
 
         if (likely(ret == NET_XMIT_SUCCESS)) {
@@ -241,56 +282,35 @@ static unsigned int netem_drop(struct Qdisc* sch)
         return len;
 }
 
-/* Dequeue packet.
- *  Move all packets that are ready to send from the delay holding
- *  list to the underlying qdisc, then just call dequeue
- */
 static struct sk_buff *netem_dequeue(struct Qdisc *sch)
 {
         struct netem_sched_data *q = qdisc_priv(sch);
         struct sk_buff *skb;
+        int pending;
+
+        pending = netem_run(sch);
 
         skb = q->qdisc->dequeue(q->qdisc);
-        if (skb) 
+        if (skb) {
+                pr_debug("netem_dequeue: return skb=%p\n", skb);
                 sch->q.qlen--;
+                sch->flags &= ~TCQ_F_THROTTLED;
+        }
+        else if (pending) {
+                pr_debug("netem_dequeue: throttling\n");
+                sch->flags |= TCQ_F_THROTTLED;
+        } 
+
         return skb;
 }
 
 static void netem_watchdog(unsigned long arg)
 {
         struct Qdisc *sch = (struct Qdisc *)arg;
-        struct netem_sched_data *q = qdisc_priv(sch);
-        struct net_device *dev = sch->dev;
-        struct sk_buff *skb;
-        psched_time_t now;
 
-        pr_debug("netem_watchdog: fired @%lu\n", jiffies);
-
-        spin_lock_bh(&dev->queue_lock);
-        PSCHED_GET_TIME(now);
-
-        while ((skb = skb_peek(&q->delayed)) != NULL) {
-                const struct netem_skb_cb *cb
-                        = (const struct netem_skb_cb *)skb->cb;
-                long delay 
-                        = PSCHED_US2JIFFIE(PSCHED_TDIFF(cb->time_to_send, now));
-                pr_debug("netem_watchdog: skb %p@%lu %ld\n",
-                         skb, jiffies, delay);
-
-                /* if more time remaining? */
-                if (delay > 0) {
-                        mod_timer(&q->timer, jiffies + delay);
-                        break;
-                }
-                __skb_unlink(skb, &q->delayed);
-
-                if (q->qdisc->enqueue(skb, q->qdisc)) {
-                        sch->q.qlen--;
-                        sch->qstats.drops++;
-                }
-        }
-        qdisc_run(dev);
-        spin_unlock_bh(&dev->queue_lock);
+        pr_debug("netem_watchdog qlen=%d\n", sch->q.qlen);
+        sch->flags &= ~TCQ_F_THROTTLED;
+        netif_schedule(sch->dev);
 }
 
 static void netem_reset(struct Qdisc *sch)
@@ -301,6 +321,7 @@ static void netem_reset(struct Qdisc *sch)
         skb_queue_purge(&q->delayed);
 
         sch->q.qlen = 0;
+        sch->flags &= ~TCQ_F_THROTTLED;
         del_timer_sync(&q->timer);
 }