Re: 5.15-rc3+ crash in fq-codel?

On 9/29/21 4:48 PM, Ben Greear wrote:

On 9/29/21 4:42 PM, Eric Dumazet wrote:

quoted

On 9/29/21 4:28 PM, Eric Dumazet wrote:

quoted

quoted

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.

Thanks,
Ben