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

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Date: Thu, 7 Dec 2023 11:16:10 +0100
From: Przemek Kitszel <przemyslaw.kitszel@...el.com>
To: Johannes Berg <johannes@...solutions.net>, Jakub Kicinski
	<kuba@...nel.org>
CC: <netdev@...r.kernel.org>, Heiner Kallweit <hkallweit1@...il.com>, "Marc
 MERLIN" <marc@...lins.org>, "intel-wired-lan@...ts.osuosl.org"
	<intel-wired-lan@...ts.osuosl.org>
Subject: Re: [PATCH net v3] net: ethtool: do runtime PM outside RTNL

On 12/6/23 17:46, Johannes Berg wrote:
> 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
> 

I have let know our igc TL, architect, and anybody that could be
interested via cc: IWL.
And I'm happy that this could be done at relaxed pace thanks to Johannes