Re: [PATCH net] net: fix raising a softirq on the current cpu with rps enabled

[Eric Dumazet]

>
> Forgive me. Really I need some coffee. I made a mistake. This line
> above should be:
>
> +               if (!test_bit(NAPI_STATE_SCHED, &mysd->backlog.state))
>
> But the whole thing doesn't feel right. I need a few days to dig into
> this part until Eric can help me with more of it.
>

I am still traveling, and this is weekend time :/

It should not be too hard to read net/core/dev.c and remember that not
_all_ drivers (or some core networking functions) use the NAPI model.

eg look at netif_rx() and ask yourself why your patch is buggy.

Just look at callers of enqueue_to_backlog() and ask yourself if all
of them are called from net_rx_action()

[The answer is no, just in case you wonder]

In order to add your optimization, more work is needed, like adding
new parameters so that we do not miss critical
__raise_softirq_irqoff(NET_RX_SOFTIRQ) when _needed_.

We keep going circles around softirq deficiencies, I feel you are
trying to fix a second-order 'issue'.

Real cause is elsewhere, look at recent patches from Jakub.

Thanks.