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authorPatrick McHardy <kaber@trash.net>2007-07-14 20:49:26 -0700
committerDavid S. Miller <davem@davemloft.net>2007-07-14 20:49:26 -0700
commit0621ed2e4edbe2f6f83dafbf85eecefae7aaf2e8 (patch)
tree30e005117719da029a238b88c742b0a7e516ad50
parent59eecdfb166f6846ae356ddc744abed5820ad965 (diff)
downloadlinux-0621ed2e4edbe2f6f83dafbf85eecefae7aaf2e8.tar.bz2
[NET_SCHED]: Revert "avoid transmit softirq on watchdog wakeup" optimization
As noticed by Ranko Zivojnovic <ranko@spidernet.net>, calling qdisc_run from the timer handler can result in deadlock: > CPU#0 > > qdisc_watchdog() fires and gets dev->queue_lock > qdisc_run()...qdisc_restart()... > -> releases dev->queue_lock and enters dev_hard_start_xmit() > > CPU#1 > > tc del qdisc dev ... > qdisc_graft()...dev_graft_qdisc()...dev_deactivate()... > -> grabs dev->queue_lock ... > > qdisc_reset()...{cbq,hfsc,htb,netem,tbf}_reset()...qdisc_watchdog_cancel()... > -> hrtimer_cancel() - waiting for the qdisc_watchdog() to exit, while still > holding dev->queue_lock > > CPU#0 > > dev_hard_start_xmit() returns ... > -> wants to get dev->queue_lock(!) > > DEADLOCK! The entire optimization is a bit questionable IMO, it moves potentially large parts of NET_TX_SOFTIRQ work to TIMER_SOFTIRQ/HRTIMER_SOFTIRQ, which kind of defeats the separation of them. Signed-off-by: Patrick McHardy <kaber@trash.net> Acked-by: Ranko Zivojnovic <ranko@spidernet.net> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/sched/sch_api.c6
1 files changed, 1 insertions, 5 deletions
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index d92ea26982c5..4fd0beca9450 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -278,11 +278,7 @@ static enum hrtimer_restart qdisc_watchdog(struct hrtimer *timer)
wd->qdisc->flags &= ~TCQ_F_THROTTLED;
smp_wmb();
- if (spin_trylock(&dev->queue_lock)) {
- qdisc_run(dev);
- spin_unlock(&dev->queue_lock);
- } else
- netif_schedule(dev);
+ netif_schedule(dev);
return HRTIMER_NORESTART;
}