netdev - Re: [net-next PATCH] hsr: Simplify code for announcing HSR nodes timer setup

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Date: Fri, 26 Apr 2024 17:33:17 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Lukasz Majewski <lukma@...x.de>
Cc: netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>, Casper
 Andersson <casper.casan@...il.com>, Andrew Lunn <andrew@...n.ch>, Eric
 Dumazet <edumazet@...gle.com>, Vladimir Oltean <olteanv@...il.com>, "David
 S. Miller" <davem@...emloft.net>, Oleksij Rempel <o.rempel@...gutronix.de>,
 Tristram.Ha@...rochip.com, Sebastian Andrzej Siewior
 <bigeasy@...utronix.de>, Ravi Gunasekaran <r-gunasekaran@...com>, Simon
 Horman <horms@...nel.org>, Nikita Zhandarovich <n.zhandarovich@...tech.ru>,
 Murali Karicheri <m-karicheri2@...com>, Jiri Pirko <jiri@...nulli.us>, Dan
 Carpenter <dan.carpenter@...aro.org>, Ziyang Xuan
 <william.xuanziyang@...wei.com>, Shigeru Yoshida <syoshida@...hat.com>,
 "Ricardo B. Marliere" <ricardo@...liere.net>, linux-kernel@...r.kernel.org
Subject: Re: [net-next PATCH] hsr: Simplify code for announcing HSR nodes
 timer setup

On Thu, 25 Apr 2024 17:39:58 +0200 Lukasz Majewski wrote:
> Up till now the code to start HSR announce timer, which triggers sending
> supervisory frames, was assuming that hsr_netdev_notify() would be called
> at least twice for hsrX interface. This was required to have different
> values for old and current values of network device's operstate.
> 
> This is problematic for a case where hsrX interface is already in the
> operational state when hsr_netdev_notify() is called, so timer is not
> configured to trigger and as a result the hsrX is not sending supervisory
> frames to HSR ring.
> 
> This error has been discovered when hsr_ping.sh script was run. To be
> more specific - for the hsr1 and hsr2 the hsr_netdev_notify() was
> called at least twice with different IF_OPER_{LOWERDOWN|DOWN|UP} states
> assigned in hsr_check_carrier_and_operstate(hsr). As a result there was
> no issue with sending supervisory frames.
> However, with hsr3, the notify function was called only once with
> operstate set to IF_OPER_UP and timer responsible for triggering
> supervisory frames was not fired.
> 
> The solution is to use netif_oper_up() helper function to assess if
> network device is up and then setup timer. Otherwise the timer is
> activated.

NETDEV_CHANGE can get called for multiple trivial reasons, if the timer
is already running we'll mess with the spacing of the frames, no?

If there is a path where the device may get activated without the
notifier firing - maybe we can check carrier there and schedule the
timer?

Also sounds like a bug fix, so please add a Fixes tag.