Re: Regression: Failed boots bisected to 4cd13c21b207 "softirq: Let ksoftirqd do its job"

[Brian Starkey]

Hi,

On Wed, Nov 23, 2016 at 12:03:28PM -0800, Eric Dumazet wrote:
> On Wed, Nov 23, 2016 at 10:21 AM, Brian Starkey <brian.starkey@xxxxxxx> wrote:
>
> > This patch didn't help.
> >
> > I did get some new traces though - I've attached the diff for the
> > trace_printks I added.
> >
> > Before 4cd13c21b207:
> > https://drive.google.com/open?id=0B8siaK6ZjvEwcEtOeFQzTmY0Nnc
> > After 4cd13c21b207:
> > https://drive.google.com/open?id=0B8siaK6ZjvEwZnQ4MVg1d3d1Tm8
> >
> > It looks like the difference is that after 4cd13c21b207 the RX softirq
> > isn't running, and RX interrupts don't call softirq_raise anymore -
> > presumably because there's one pending, but I didn't have time to
> > track that down to a code-path.
> >
> > Cheers,
> > -Brian
>
> Hi Brian
>
> Looks like netif_rx() drops the incoming packets then ?
>
> Maybe netif_running() is not happy :(
>
> Could you trace netif_rx() return value (NET_RX_SUCCESS or NET_RX_DROP)

Some packets are dropped, but not very many:

  $ grep NET_RX_SUCCESS trace_netif_rx.txt | wc -l
  14399
  $ grep NET_RX_DROP trace_netif_rx.txt | wc -l
  22

Without the ksoftirqd change there were zero NET_RX_DROPs.

-Brian

> Thanks !