[NET_SCHED] qdisc: avoid transmit softirq on watchdog wakeup

If possible, avoid having to do a transmit softirq when a qdisc
watchdog decides to re-enable.  The watchdog routine runs off
a timer, so it is already in the same effective context as
the softirq.

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

1 files changed, 7 insertions, 1 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index fcaa4adefc82..58732509160d 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -296,10 +296,16 @@ static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer)
 {
         struct qdisc_watchdog *wd = container_of(timer, struct qdisc_watchdog,
                                                  timer);
+        struct net_device *dev = wd->qdisc->dev;
 
         wd->qdisc->flags &= ~TCQ_F_THROTTLED;
         smp_wmb();
-        netif_schedule(wd->qdisc->dev);
+        if (spin_trylock(&dev->queue_lock)) {
+                qdisc_run(dev);
+                spin_unlock(&dev->queue_lock);
+        } else
+                netif_schedule(dev);
+
         return HRTIMER_NORESTART;
 }