From: John Fastabend <john.fastabend@gmail.com>
To: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>,
Dave Taht <dave.taht@gmail.com>
Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
"David S. Miller" <davem@davemloft.net>,
"linux-can@vger.kernel.org" <linux-can@vger.kernel.org>,
Martin Elshuber <martin.elshuber@theobroma-systems.com>
Subject: Re: [bug, bisected] pfifo_fast causes packet reordering
Date: Wed, 21 Mar 2018 13:52:42 -0700 [thread overview]
Message-ID: <ffdc6ca9-bf64-5514-bac9-7b107f9b443b@gmail.com> (raw)
In-Reply-To: <983427eb-2e25-f201-c953-4cff22569deb@theobroma-systems.com>
On 03/21/2018 12:44 PM, Jakob Unterwurzacher wrote:
> On 21.03.18 19:43, John Fastabend wrote:
>> Thats my theory at least. Are you able to test a patch if I generate
>> one to fix this?
>
> Yes, no problem.
Can you try this,
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index d4907b5..1e596bd 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -30,6 +30,7 @@ struct qdisc_rate_table {
enum qdisc_state_t {
__QDISC_STATE_SCHED,
__QDISC_STATE_DEACTIVATED,
+ __QDISC_STATE_RUNNING,
};
struct qdisc_size_table {
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 190570f..cf7c37d 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -377,20 +377,26 @@ static inline bool qdisc_restart(struct Qdisc *q, int *packets)
struct netdev_queue *txq;
struct net_device *dev;
struct sk_buff *skb;
- bool validate;
+ bool more, validate;
/* Dequeue packet */
+ if (test_and_set_bit(__QDISC_STATE_RUNNING, &q->state))
+ return false;
+
skb = dequeue_skb(q, &validate, packets);
- if (unlikely(!skb))
+ if (unlikely(!skb)) {
+ clear_bit(__QDISC_STATE_RUNNING, &q->state);
return false;
+ }
if (!(q->flags & TCQ_F_NOLOCK))
root_lock = qdisc_lock(q);
dev = qdisc_dev(q);
txq = skb_get_tx_queue(dev, skb);
-
- return sch_direct_xmit(skb, q, dev, txq, root_lock, validate);
+ more = sch_direct_xmit(skb, q, dev, txq, root_lock, validate);
+ clear_bit(__QDISC_STATE_RUNNING, &q->state);
+ return more;
}
>
> I just tested with the flag change you suggested (see below, I had to keep TCQ_F_CPUSTATS to prevent a crash) and I have NOT seen OOO so far.
>
Right because the code expects per cpu stats if the CPUSTATS flag is
removed it will crash.
> Thanks,
> Jakob
>
>
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index 190570f21b20..51b68ef4977b 100644
> --- a/net/sched/sch_generic.c
> +++ b/net/sched/sch_generic.c
> @@ -792,7 +792,7 @@ struct Qdisc_ops pfifo_fast_ops __read_mostly = {
> .dump = pfifo_fast_dump,
> .change_tx_queue_len = pfifo_fast_change_tx_queue_len,
> .owner = THIS_MODULE,
> - .static_flags = TCQ_F_NOLOCK | TCQ_F_CPUSTATS,
> + .static_flags = TCQ_F_CPUSTATS,
> };
> EXPORT_SYMBOL(pfifo_fast_ops);
next prev parent reply other threads:[~2018-03-21 20:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-13 18:24 [bug, bisected] pfifo_fast causes packet reordering Jakob Unterwurzacher
2018-03-13 18:35 ` Dave Taht
2018-03-14 4:03 ` John Fastabend
2018-03-14 10:09 ` Jakob Unterwurzacher
2018-03-15 18:08 ` Jakob Unterwurzacher
2018-03-15 22:30 ` John Fastabend
2018-03-16 10:26 ` Jakob Unterwurzacher
2018-03-19 6:07 ` Alexander Stein
2018-03-19 12:32 ` Paolo Abeni
2018-03-19 12:56 ` Jakob Unterwurzacher
2018-03-21 10:01 ` Jakob Unterwurzacher
2018-03-21 18:43 ` John Fastabend
2018-03-21 19:44 ` Jakob Unterwurzacher
2018-03-21 20:52 ` John Fastabend [this message]
2018-03-22 10:16 ` Jakob Unterwurzacher
2018-03-24 14:26 ` John Fastabend
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