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Message-ID: <aed988a09cb4347ec7ac1b682c4ee53b7d2a840b.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: Nuno Sa <nuno.sa@analog.com>, Greg Kroah-Hartman
 <gregkh@linuxfoundation.org>, "Rafael J. Wysocki" <rafael@kernel.org>,
 Frank Rowand <frowand.list@gmail.com>, Rob Herring <robh+dt@kernel.org>,
 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>
Cc: linux-acpi@vger.kernel.org, devicetree@vger.kernel.org, 
	linux-kernel@vger.kernel.org
Date: Mon, 12 Feb 2024 13:10:27 +0100
In-Reply-To: <20240205-fix-device-links-overlays-v2-2-5344f8c79d57@analog.com>
References: 
	<20240205-fix-device-links-overlays-v2-0-5344f8c79d57@analog.com>
	 <20240205-fix-device-links-overlays-v2-2-5344f8c79d57@analog.com>
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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 attached to
> these devices will also be dropped asynchronously and so we cannot
> guarantee the DT overlay assumption that the of_node refcount must be 1 i=
n
> __of_changeset_entry_destroy().
>=20
> Given the above, call the new fwnode_links_flush_queue() helper to flush
> the devlink workqueue so we can be sure that all links are dropped 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>
> =C2=A0
> =C2=A0#include "of_private.h"
> =C2=A0
> @@ -518,6 +519,13 @@ EXPORT_SYMBOL(of_changeset_create_node);
> =C2=A0
> =C2=A0static void __of_changeset_entry_destroy(struct of_changeset_entry =
*ce)
> =C2=A0{
> +	/*
> +	 * device links drop their device references (and hence their of_node
> +	 * references) asynchronously on a dedicated workqueue. Hence we need
> +	 * to flush it to make sure everything is done before doing the below
> +	 * checks.
> +	 */
> +	fwnode_links_flush_queue();
> =C2=A0	if (ce->action =3D=3D OF_RECONFIG_ATTACH_NODE &&
> =C2=A0	=C2=A0=C2=A0=C2=A0 of_node_check_flag(ce->np, OF_OVERLAY)) {
> =C2=A0		if (kref_read(&ce->np->kobj.kref) > 1) {
>=20

Hi Rob and Frank,

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.

Thanks!
- Nuno S=C3=A1