On Wed, 2015-11-04 at 06:25 +0200, Denys Fedoryshchenko wrote:
> On 2015-11-04 00:06, Cong Wang wrote:
> > On Mon, Nov 2, 2015 at 6:11 AM, Denys Fedoryshchenko
> > <nuclear...@nuclearcat.com> wrote:
> >> Hi!
> >>
> >> Actually seems i was getting this panic for a while (once per week) on
> >> loaded pppoe server, but just now was able to get full panic message.
> >> After checking commit logs on sch_fq.c i didnt seen any fixes, so
> >> probably
> >> upgrading to newer kernel wont help?
> >
> >
> > Can you share your `tc qdisc show dev xxxx` with us? And how to
> > reproduce
> > it? I tried to setup htb+fq and then flip the interface back and forth
> > but I don't
> > see any crash.
> My guess it wont be easy to reproduce, it is happening on box with 4.5k
> interfaces, that constantly create/delete interfaces,
> and even with that this problem may happen once per day, or may not
> happen for 1 week.
>
> Here is script that is being fired after new ppp interface detected. But
> pppoe process are independent from
> process that are "establishing" shapers.
It is probably a generic bug. sch_fq seems OK to me.
Somehow nobody tries to change qdisc hundred times per second ;)
Could you try following patch ?
It seems to 'fix' the issue for me.
diff --git a/net/core/dev.c b/net/core/dev.c
index 8ce3f74cd6b9..bf136103bc7b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2880,6 +2880,12 @@ static inline int __dev_xmit_skb(struct sk_buff *skb,
struct Qdisc *q,
spin_lock(&q->busylock);
spin_lock(root_lock);
+ if (unlikely(q != rcu_dereference_bh(txq->qdisc))) {
+ pr_err_ratelimited("Arg, qdisc changed ! state %lx\n",
q->state);
+ kfree_skb(skb);
+ rc = NET_XMIT_DROP;
+ goto end;
+ }
if (unlikely(test_bit(__QDISC_STATE_DEACTIVATED, &q->state))) {
kfree_skb(skb);
rc = NET_XMIT_DROP;
@@ -2913,6 +2919,7 @@ static inline int __dev_xmit_skb(struct sk_buff *skb,
struct Qdisc *q,
__qdisc_run(q);
}
}
+end:
spin_unlock(root_lock);
if (unlikely(contended))
spin_unlock(&q->busylock);
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