netdev - Re: [PATCH net-next v2 2/3] net: dsa: add Arrow SpeedChips XRS700x driver

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Message-ID: <20201127155649.5ce7ed82@kicinski-fedora-pc1c0hjn.DHCP.thefacebook.com>
Date:   Fri, 27 Nov 2020 15:56:49 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        George McCollister <george.mccollister@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        "open list:OPEN FIRMWARE AND..." <devicetree@...r.kernel.org>
Subject: Re: [PATCH net-next v2 2/3] net: dsa: add Arrow SpeedChips XRS700x
 driver

What is it with my email today, didn't get this one again.

On Sat, 28 Nov 2020 01:39:16 +0200 Vladimir Oltean wrote:
> On Sat, Nov 28, 2020 at 12:30:48AM +0100, Andrew Lunn wrote:
> > > If there is a better alternative I'm all ears but having /proc and
> > > ifconfig return zeros for error counts while ip link doesn't will lead
> > > to too much confusion IMO. While delayed update of stats is a fact of
> > > life for _years_ now (hence it was backed into the ethtool -C API).  
> > 
> > How about dev_seq_start() issues a netdev notifier chain event, asking
> > devices which care to update their cached rtnl_link_stats64 counters.
> > They can decide if their cache is too old, and do a blocking read for
> > new values.

Just to avoid breaking the suggestion that seqfiles don't sleep after
.start? Hm. I thought BPF slept (or did cond_reshed()) in the middle of
seq iteration. We should double check that seqfiles really can't sleep.

> > Once the notifier has completed, dev_seq_start() can then
> > rcu_read_lock() and do the actual collection of stats from the drivers
> > non-blocking.