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

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Date:   Wed, 19 May 2021 12:51:07 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Lijun Pan <ljp@...ux.vnet.ibm.com>
Cc:     saeedm@...dia.com, David Miller <davem@...emloft.net>,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next] mlx5: count all link events

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.