Re: [PATCH net-next] sh_eth: remove open coded netif_running()

[Geert Uytterhoeven]

Hi Sergey,

On Wed, Mar 22, 2023 at 9:54 PM Sergey Shtylyov <s.shtylyov@xxxxxx> wrote:
> On 3/21/23 9:58 AM, Wolfram Sang wrote:
> > It had a purpose back in the days, but today we have a handy helper.
>
>    Well, the is_opened flag doesn't get set/cleared at the same time as
> __LINK_STATE_START. I'm not sure they are interchangeable...
>
> > Reported-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> > Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>

> > --- a/drivers/net/ethernet/renesas/sh_eth.c
> > +++ b/drivers/net/ethernet/renesas/sh_eth.c
> > @@ -2441,8 +2441,6 @@ static int sh_eth_open(struct net_device *ndev)
> >
> >       netif_start_queue(ndev);
> >
> > -     mdp->is_opened = 1;
> > -
>
>    __LINK_STATE_START gets set before the ndo_open() method call, so
> before the RPM call that enbales the clocks...
>
> >       return ret;
> >
> >  out_free_irq:
> > @@ -2565,7 +2563,7 @@ static struct net_device_stats *sh_eth_get_stats(struct net_device *ndev)
> >       if (mdp->cd->no_tx_cntrs)
> >               return &ndev->stats;
> >
> > -     if (!mdp->is_opened)
> > +     if (!netif_running(ndev))
> >               return &ndev->stats;
>
>    I guess mdp->is_opened is checked here to avoid reading the counter
> regs when RPM hasn't been called yet to enable the clocks...

Exactly, cfr. commit 7fa2955ff70ce453 ("sh_eth: Fix sleeping function
called from invalid context").

So you mean sh_eth_get_stats() can now be called after setting
__LINK_STATE_START, but before RPM has enabled the clocks?
Is there some protection against parallel execution of ndo_open()
and get_stats()?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds