From: Eric Dumazet <eric.dumazet@gmail.com>
To: Ben Greear <greearb@candelatech.com>, netdev <netdev@vger.kernel.org>
Subject: Re: 5.15-rc3+ crash in fq-codel?
Date: Wed, 29 Sep 2021 17:40:06 -0700 [thread overview]
Message-ID: <aa633585-0f0d-edf2-5659-72a49c1061c6@gmail.com> (raw)
In-Reply-To: <c4000c2a-8894-c3f5-9497-82bce4615be1@gmail.com>
On 9/29/21 5:29 PM, Eric Dumazet wrote:
>
>
> On 9/29/21 5:04 PM, Ben Greear wrote:
>> On 9/29/21 4:48 PM, Ben Greear wrote:
>>> On 9/29/21 4:42 PM, Eric Dumazet wrote:
>>>>
>>>>
>>>> On 9/29/21 4:28 PM, Eric Dumazet wrote:
>>>>>
>>>>
>>>>>
>>>>> Actually the bug seems to be in pktgen, vs NET_XMIT_CN
>>>>>
>>>>> You probably would hit the same issues with other qdisc also using NET_XMIT_CN
>>>>>
>>>>
>>>> I would try the following patch :
>>>>
>>>> diff --git a/net/core/pktgen.c b/net/core/pktgen.c
>>>> index a3d74e2704c42e3bec1aa502b911c1b952a56cf1..0a2d9534f8d08d1da5dfc68c631f3a07f95c6f77 100644
>>>> --- a/net/core/pktgen.c
>>>> +++ b/net/core/pktgen.c
>>>> @@ -3567,6 +3567,7 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
>>>> case NET_XMIT_DROP:
>>>> case NET_XMIT_CN:
>>>> /* skb has been consumed */
>>>> + pkt_dev->last_ok = 1;
>>>> pkt_dev->errors++;
>>>> break;
>>>> default: /* Drivers are not supposed to return other values! */
>>
>> While patching my variant of pktgen, I took a look at the 'default' case. I think
>> it should probably go above NET_XMIT_DROP and fallthrough into the consumed pkt path?
>>
>> Although, probably not a big deal since only bugs elsewhere would hit that path, and
>> we don't really know if skb would be consumed in that case or not.
>>
>
> This is probably dead code after commit
>
> commit f466dba1832f05006cf6caa9be41fb98d11cb848 pktgen: ndo_start_xmit can return NET_XMIT_xxx values
>
> So this does not really matter anymore.
>
>
Alternative would be the following patch.
NET_XMIT_CN means the packet has been queued for transmit,
but that we might have dropped prior packets.
Probably not a big deal to make the difference in pktgen.
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index a3d74e2704c42e3bec1aa502b911c1b952a56cf1..5c612cbc74c790f64aff5ce602843378284c7119 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -3557,6 +3557,7 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
switch (ret) {
case NETDEV_TX_OK:
+ case NET_XMIT_CN:
pkt_dev->last_ok = 1;
pkt_dev->sofar++;
pkt_dev->seq_num++;
@@ -3565,8 +3566,8 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)
goto xmit_more;
break;
case NET_XMIT_DROP:
- case NET_XMIT_CN:
/* skb has been consumed */
+ pkt_dev->last_ok = 1;
pkt_dev->errors++;
break;
default: /* Drivers are not supposed to return other values! */
next prev parent reply other threads:[~2021-09-30 0:40 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-27 23:30 5.15-rc3+ crash in fq-codel? Ben Greear
2021-09-27 23:49 ` Eric Dumazet
2021-09-28 0:04 ` Ben Greear
2021-09-28 0:16 ` Ben Greear
2021-09-28 22:00 ` Ben Greear
2021-09-28 23:25 ` Eric Dumazet
2021-09-29 19:07 ` Ben Greear
2021-09-29 23:21 ` Eric Dumazet
2021-09-29 23:28 ` Eric Dumazet
2021-09-29 23:42 ` Eric Dumazet
2021-09-29 23:48 ` Ben Greear
2021-09-30 0:04 ` Ben Greear
2021-09-30 0:29 ` Eric Dumazet
2021-09-30 0:40 ` Eric Dumazet [this message]
2021-09-30 1:36 ` Ben Greear
2021-09-30 16:44 ` Ben Greear
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aa633585-0f0d-edf2-5659-72a49c1061c6@gmail.com \
--to=eric.dumazet@gmail.com \
--cc=greearb@candelatech.com \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).