linux-kernel - Re: [PATCH] Revert "net: linkwatch: add check for netdevice being present to linkwatch_do

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Date:   Fri, 18 Sep 2020 10:58:49 -0700
From:   Saeed Mahameed <saeed@...nel.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Gaku Inami <gaku.inami.xh@...esas.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "net: linkwatch: add check for netdevice being
 present to linkwatch_do_dev"

On Tue, 2020-09-01 at 17:02 +0200, Geert Uytterhoeven wrote:
> This reverts commit 124eee3f6955f7aa19b9e6ff5c9b6d37cb3d1e2c.
> 
> Inami-san reported that this commit breaks bridge support in a Xen
> environment, and that reverting it fixes this.
> 
> During system resume, bridge ports are no longer enabled, as that
> relies
> on the receipt of the NETDEV_CHANGE notification.  This notification
> is
> not sent, as netdev_state_change() is no longer called.
> 
> Note that the condition this commit intended to fix never existed
> upstream, as the patch triggering it and referenced in the commit was
> never applied upstream.  Hence I can confirm s2ram on r8a73a4/ape6evm
> and sh73a0/kzm9g works fine before/after this revert.
> 
> Reported-by Gaku Inami <gaku.inami.xh@...esas.com>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
>  net/core/link_watch.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/link_watch.c b/net/core/link_watch.c
> index 75431ca9300fb9c4..c24574493ecf95e6 100644
> --- a/net/core/link_watch.c
> +++ b/net/core/link_watch.c
> @@ -158,7 +158,7 @@ static void linkwatch_do_dev(struct net_device
> *dev)
>  	clear_bit(__LINK_STATE_LINKWATCH_PENDING, &dev->state);
>  
>  	rfc2863_policy(dev);
> -	if (dev->flags & IFF_UP && netif_device_present(dev)) {
> +	if (dev->flags & IFF_UP) {

So with your issue the devices is both IFF_UP and !present ? how so ?
I think you should look into that.

I am ok with removing the "dev present" check from here just because we
shouldn't  be expecting IFF_UP && !present .. such thing must be a bug
somewhere else.

>  		if (netif_carrier_ok(dev))
>  			dev_activate(dev);
>  		else