linux-kernel - Re: [PATCH v3] driver core: fw_devlink: Stop trying to optimize cycle detection logic

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Message-ID: <CAMuHMdWaBn9PuEqiH2dekDzOLXeqn1KTT_x3qq7Zk_KUxg2qeQ@mail.gmail.com>
Date: Wed, 4 Dec 2024 13:52:56 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: Saravana Kannan <saravanak@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Francesco <francesco.dolcini@...adex.com>, 
	Tomi Valkeinen <tomi.valkeinen@...asonboard.com>, kernel-team@...roid.com, 
	linux-kernel@...r.kernel.org, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Conor Dooley <conor@...nel.org>, 
	Hervé Codina <herve.codina@...tlin.com>
Subject: Re: [PATCH v3] driver core: fw_devlink: Stop trying to optimize cycle
 detection logic

Hi Luca,

On Wed, Dec 4, 2024 at 12:48 PM Luca Ceresoli <luca.ceresoli@...tlin.com> wrote:
> On Wed, 30 Oct 2024 10:10:07 -0700
> Saravana Kannan <saravanak@...gle.com> wrote:
>
> > In attempting to optimize fw_devlink runtime, I introduced numerous cycle
> > detection bugs by foregoing cycle detection logic under specific
> > conditions. Each fix has further narrowed the conditions for optimization.
> >
> > It's time to give up on these optimization attempts and just run the cycle
> > detection logic every time fw_devlink tries to create a device link.
> >
> > The specific bug report that triggered this fix involved a supplier fwnode
> > that never gets a device created for it. Instead, the supplier fwnode is
> > represented by the device that corresponds to an ancestor fwnode.
> >
> > In this case, fw_devlink didn't do any cycle detection because the cycle
> > detection logic is only run when a device link is created between the
> > devices that correspond to the actual consumer and supplier fwnodes.
> >
> > With this change, fw_devlink will run cycle detection logic even when
> > creating SYNC_STATE_ONLY proxy device links from a device that is an
> > ancestor of a consumer fwnode.
> >
> > Reported-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> > Closes: https://lore.kernel.org/all/1a1ab663-d068-40fb-8c94-f0715403d276@ideasonboard.com/
> > Fixes: 6442d79d880c ("driver core: fw_devlink: Improve detection of overlapping cycles")
> > Tested-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
>
> After rebasing my work for the hotplug connector driver using device
> tree overlays [0] on v6.13-rc1 I started getting these OF errors on
> overlay removal:
>
> OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/panel-dsi-lvds
> OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/backlight-addon
> OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/battery-charger
> OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-5v0-sys
> OF: ERROR: memory leak, expected refcount 1 instead of 2, of_node_get()/of_node_put() unbalanced - destroy cset entry: attach overlay node /addon-connector/devices/regulator-addon-3v3-sys
>
> ...and many more. Exactly one per each device in the overlay 'devices'
> node, each implemented by a platform driver.

FTR, I am not seeing that when loading/removing
r8a77990-ebisu-cn41-msiof0-25lc040.dtso
https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git/commit/?h=topic/renesas-overlays&id=dd998e8db58b67744eb91f11f13544401c975470

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds