netdev - Re: [PATCH net-next] mlx5: count all link events

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Date:   Wed, 19 May 2021 13:18:36 -0700
From:   Saeed Mahameed <saeed@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>,
        Lijun Pan <ljp@...ux.vnet.ibm.com>
Cc:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] mlx5: count all link events

On Wed, 2021-05-19 at 12:51 -0700, Jakub Kicinski wrote:
> On Wed, 19 May 2021 14:34:34 -0500 Lijun Pan wrote:
> > Is it possible to integrate netif_carrier_event into
> > netif_carrier_on? like,
> > 
> > 
> > void netif_carrier_on(struct net_device *dev)
> > {
> >         if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state))
> > {
> >                 if (dev->reg_state == NETREG_UNINITIALIZED)
> >                         return;
> >                 atomic_inc(&dev->carrier_up_count);
> >                 linkwatch_fire_event(dev);
> >                 if (netif_running(dev))
> >                         __netdev_watchdog_up(dev);
> >         } else {
> >                 if (dev->reg_state == NETREG_UNINITIALIZED)
> >                         return;
> >                 atomic_inc(&dev->carrier_down_count);
> >                 atomic_inc(&dev->carrier_up_count);
> >         }
> > }
> > EXPORT_SYMBOL(netif_carrier_on);
> 
> Ah, I meant to address that in the commit message, thanks for bringing
> this up. I suspect drivers may depend on the current behavior of
> netif_carrier_on()/off() being idempotent. We have no real reason for
> removing that assumption.
> 
> I assumed netif_carrier_event() would be used specifically in places
> driver is actually servicing a link event from the device, and
> therefore is relatively certain that _something_ has happened.

then according to the above assumption it is safe to make
netif_carrier_event() do everything.

netif_carrier_event(netdev, up) {
	if (dev->reg_state == NETREG_UNINITIALIZED)
		return;

	if (up == netif_carrier_ok(netdev) {
		atomic_inc(&netdev->carrier_up_count);
		atomic_inc(&netdev->carrier_down_count);
		linkwatch_fire_event(netdev);
	}

	if (up) {
		netdev_info(netdev, "Link up\n");
		netif_carrier_on(netdev);
	} else {
		netdev_info(netdev, "Link down\n");
		netif_carrier_off(netdev);
	}
}