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Message-ID: <71fa22870246c4ed6ae9cbb2cb93db557dd855f7.camel@gmail.com>
Subject: Re: [PATCH v2 2/2] of: dynamic: flush devlinks workqueue before
 destroying the changeset
From: Nuno =?ISO-8859-1?Q?S=E1?= <noname.nuno@gmail.com>
To: Saravana Kannan <saravanak@google.com>
Cc: Rob Herring <robh@kernel.org>, Nuno Sa <nuno.sa@analog.com>, Greg
 Kroah-Hartman <gregkh@linuxfoundation.org>, "Rafael J. Wysocki"
 <rafael@kernel.org>, Frank Rowand <frowand.list@gmail.com>, Andy Shevchenko
 <andriy.shevchenko@linux.intel.com>,  Daniel Scally <djrscally@gmail.com>,
 Heikki Krogerus <heikki.krogerus@linux.intel.com>, Sakari Ailus
 <sakari.ailus@linux.intel.com>, Len Brown <lenb@kernel.org>, 
 linux-acpi@vger.kernel.org, devicetree@vger.kernel.org, 
 linux-kernel@vger.kernel.org, Android Kernel Team <kernel-team@android.com>
Date: Wed, 14 Feb 2024 13:51:29 +0100
In-Reply-To: <CAGETcx9xgLykm7Ti-A4+sYxQkn=KTUptW9fbFxgTcceihutwRQ@mail.gmail.com>
References: 
	<20240205-fix-device-links-overlays-v2-0-5344f8c79d57@analog.com>
	 <20240205-fix-device-links-overlays-v2-2-5344f8c79d57@analog.com>
	 <aed988a09cb4347ec7ac1b682c4ee53b7d2a840b.camel@gmail.com>
	 <20240213145131.GA1180152-robh@kernel.org>
	 <48a86fa6908a2a7a38a45dc6dbb5574c4a9d7400.camel@gmail.com>
	 <CAGETcx9xgLykm7Ti-A4+sYxQkn=KTUptW9fbFxgTcceihutwRQ@mail.gmail.com>
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On Tue, 2024-02-13 at 19:44 -0800, Saravana Kannan wrote:
> On Tue, Feb 13, 2024 at 6:57=E2=80=AFAM Nuno S=C3=A1 <noname.nuno@gmail.c=
om> wrote:
> >=20
> > On Tue, 2024-02-13 at 08:51 -0600, Rob Herring wrote:
> > > On Mon, Feb 12, 2024 at 01:10:27PM +0100, Nuno S=C3=A1 wrote:
> > > > On Mon, 2024-02-05 at 13:09 +0100, Nuno Sa wrote:
> > > > > Device links will drop their supplier + consumer refcounts
> > > > > asynchronously. That means that the refcount of the of_node attac=
hed
> > > > > to
> > > > > these devices will also be dropped asynchronously and so we canno=
t
> > > > > guarantee the DT overlay assumption that the of_node refcount mus=
t be
> > > > > 1 in
> > > > > __of_changeset_entry_destroy().
> > > > >=20
> > > > > Given the above, call the new fwnode_links_flush_queue() helper t=
o
> > > > > flush
> > > > > the devlink workqueue so we can be sure that all links are droppe=
d
> > > > > before
> > > > > doing the proper checks.
> > > > >=20
> > > > > Signed-off-by: Nuno Sa <nuno.sa@analog.com>
> > > > > ---
> > > > > =C2=A0drivers/of/dynamic.c | 8 ++++++++
> > > > > =C2=A01 file changed, 8 insertions(+)
> > > > >=20
> > > > > diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
> > > > > index 3bf27052832f..b7153c72c9c9 100644
> > > > > --- a/drivers/of/dynamic.c
> > > > > +++ b/drivers/of/dynamic.c
> > > > > @@ -14,6 +14,7 @@
> > > > > =C2=A0#include <linux/slab.h>
> > > > > =C2=A0#include <linux/string.h>
> > > > > =C2=A0#include <linux/proc_fs.h>
> > > > > +#include <linux/fwnode.h>
> > > > >=20
> > > > > =C2=A0#include "of_private.h"
> > > > >=20
> > > > > @@ -518,6 +519,13 @@ EXPORT_SYMBOL(of_changeset_create_node);
> > > > >=20
> > > > > =C2=A0static void __of_changeset_entry_destroy(struct of_changese=
t_entry
> > > > > *ce)
> > > > > =C2=A0{
> > > > > + /*
> > > > > +=C2=A0 * device links drop their device references (and hence th=
eir
> > > > > of_node
> > > > > +=C2=A0 * references) asynchronously on a dedicated workqueue. He=
nce we
> > > > > need
> > > > > +=C2=A0 * to flush it to make sure everything is done before doin=
g the
> > > > > below
> > > > > +=C2=A0 * checks.
> > > > > +=C2=A0 */
> > > > > + fwnode_links_flush_queue();
> > > > > =C2=A0 if (ce->action =3D=3D OF_RECONFIG_ATTACH_NODE &&
> > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 of_node_check_flag(ce->np, OF_OVER=
LAY)) {
> > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (kref_r=
ead(&ce->np->kobj.kref) > 1) {
> > > > >=20
> > > >=20
> > > > Hi Rob and Frank,
> > > >=20
> > > > Any way you could take a look at this and see if you're ok with the
> > > > change
> > > > in the
> > > > overlay code?
> > > >=20
> > > > On the devlink side , we already got the ok from Rafael.
> > >=20
> > > Didn't Saravana say he was going to look at this? As of yesterday, he=
's
> > > also a DT maintainer so deferring to him.
> > >=20
> >=20
> > Yeah, I did asked him but I guess he never had the time for it... Sarav=
ana,
> > could you please give some feedback on this? I think the most sensible =
part
> > is
> > on the devlink side but I assume this is not going to be merged without=
 an
> > ack
> > from a DT maintainer...
>=20
> Sorry for the delay Nuno. I'll get to this. I promise. This week is a bit
> busy.
>=20

No worries. Just making sure it's not forgotten :)

- Nuno S=C3=A1