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

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Date: Wed, 06 Dec 2023 10:37:56 +0100
From: Johannes Berg <johannes@...solutions.net>
To: Przemek Kitszel <przemyslaw.kitszel@...el.com>, netdev@...r.kernel.org
Cc: Marc MERLIN <marc@...lins.org>, Jesse Brandeburg
	 <jesse.brandeburg@...el.com>, Tony Nguyen <anthony.l.nguyen@...el.com>, 
	intel-wired-lan@...ts.osuosl.org, Heiner Kallweit <hkallweit1@...il.com>, 
	Aleksandr Loktionov <aleksandr.loktionov@...el.com>
Subject: Re: [RFC PATCH] net: ethtool: do runtime PM outside RTNL

On Wed, 2023-12-06 at 09:46 +0100, Przemek Kitszel wrote:
> 
> That sounds right too; one could argue if your fix is orthogonal to that
> or not. I would say that your fix makes core net code more robust
> against drivers from past millennia. :)
> igc folks are notified, no idea how much time it would take to propose
> a fix.

Maybe it should be on whoever added runtime pm to ethtool ;-)

Heiner, the igc driver was already doing this when you added
pm_runtime_get_sync() ops, was there a discussion at the time, or just
missed?

I really don't know any of this ...

> > Well, according to the checks, the patch really should use
> > netdev_get_by_name() and netdev_put()? But I don't know how to do that
> > on short-term stack thing ... maybe it doesn't have to?
> 
> Nice to have such checks :)
> You need some &netdevice_tracker, perhaps one added into struct net
> or other place that would allow to track it at ethtool level.

Yeah but that's dynamic? Seems weird to add something to allocations for
something released in the same function ...

> "short term stack thing" does not relieve us from good coding practices,
> but perhaps "you just replaced __dev_get_by_name() call by
> dev_get_by_name()" to fix a bug would ;) - with transition to tracked
> alloc as a next series to be promised :)

All I want is to know how ;)
but I guess I can try to find examples.

> anyway, I'm fresh here, and would love to know what others think about

Not me, but me too ;-)

johannes