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Message-ID: <ea13bc4f8a8aaf5b91ab3ca403533475000d5d87.camel@gmail.com>
Subject: Re: [PATCH v6 1/2] driver core: Introduce device_link_wait_removal()
From: Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Herve Codina
	 <herve.codina@bootlin.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Rob Herring
 <robh+dt@kernel.org>,  Frank Rowand <frowand.list@gmail.com>, Saravana
 Kannan <saravanak@google.com>, Lizhi Hou <lizhi.hou@amd.com>,  Max Zhen
 <max.zhen@amd.com>, Sonal Santan <sonal.santan@amd.com>, Stefano Stabellini
 <stefano.stabellini@xilinx.com>, Jonathan Cameron
 <Jonathan.Cameron@huawei.com>,  linux-kernel@vger.kernel.org,
 devicetree@vger.kernel.org, Allan Nielsen <allan.nielsen@microchip.com>,
 Horatiu Vultur <horatiu.vultur@microchip.com>,  Steen Hegelund
 <steen.hegelund@microchip.com>, Luca Ceresoli <luca.ceresoli@bootlin.com>,
 Nuno Sa <nuno.sa@analog.com>, Thomas Petazzoni
 <thomas.petazzoni@bootlin.com>,  stable@vger.kernel.org
Date: Tue, 26 Mar 2024 08:05:37 +0100
In-Reply-To: <2024032554-tipoff-extrude-a631@gregkh>
References: <20240325152140.198219-1-herve.codina@bootlin.com>
	 <20240325152140.198219-2-herve.codina@bootlin.com>
	 <2024032554-tipoff-extrude-a631@gregkh>
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On Mon, 2024-03-25 at 19:38 +0100, Greg Kroah-Hartman wrote:
> On Mon, Mar 25, 2024 at 04:21:25PM +0100, Herve Codina wrote:
> > The commit 80dd33cf72d1 ("drivers: base: Fix device link removal")
> > introduces a workqueue to release the consumer and supplier devices use=
d
> > in the devlink.
> > In the job queued, devices are release and in turn, when all the
> > references to these devices are dropped, the release function of the
> > device itself is called.
> >=20
> > Nothing is present to provide some synchronisation with this workqueue
> > in order to ensure that all ongoing releasing operations are done and
> > so, some other operations can be started safely.
> >=20
> > For instance, in the following sequence:
> > =C2=A0 1) of_platform_depopulate()
> > =C2=A0 2) of_overlay_remove()
>=20
> So this is only an issue for overlays?=C2=A0 Why has no one noticed this =
in
> the years since 80dd33cf72d1 was added?=C2=A0 Why is this an issue now
> suddenly?
>=20

Not sure either... Note this is only an issue if device links are in place.=
 So the
overlay needs to have nodes creating those links. You need to have regulato=
rs, pwm,
eth phy (at least these ones I'm aware they create links) to trigger this. =
We would
have to dig through git to understand when would this be noticeable. But no=
te this is
very straight to trigger.

May also very well be that most people don't really "play" with overlay rem=
oval...
For example, I have been dealing with overlays on rpi's for the last 5 year=
s and only
noticed this last year when we had an usecase that involved overlay removal=
.

- Nuno S=C3=A1