netdev - Re: [PATCH net v3] net: ethtool: do runtime PM outside RTNL

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Message-ID: <e6f227ee701e1ee37e8f568b1310d240a2b8935a.camel@sipsolutions.net>
Date: Wed, 06 Dec 2023 17:46:07 +0100
From: Johannes Berg <johannes@...solutions.net>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>, Marc
 MERLIN <marc@...lins.org>, Przemek Kitszel <przemyslaw.kitszel@...el.com>
Subject: Re: [PATCH net v3] net: ethtool: do runtime PM outside RTNL

On Wed, 2023-12-06 at 08:44 -0800, Jakub Kicinski wrote:
> On Wed,  6 Dec 2023 11:39:32 +0100 Johannes Berg wrote:
> > As reported by Marc MERLIN, at least one driver (igc) wants or
> > needs to acquire the RTNL inside suspend/resume ops, which can
> > be called from here in ethtool if runtime PM is enabled.
> > 
> > Allow this by doing runtime PM transitions without the RTNL
> > held. For the ioctl to have the same operations order, this
> > required reworking the code to separately check validity and
> > do the operation. For the netlink code, this now has to do
> > the runtime_pm_put a bit later.
> 
> I was really, really hoping that this would serve as a motivation
> for Intel to sort out the igb/igc implementation. The flow AFAICT
> is ndo_open() starts the NIC, the calls pm_sus, which shuts the NIC
> back down immediately (!?) then it schedules a link check from a work
> queue, which opens it again (!?). It's a source of never ending bugs.
> 

Well, I work there, but ... WiFi something else entirely. Marc just got
lucky I spotted an issue in the logs ;-)

I'll let you guys take it from here ...

johannes