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Date: Thu, 26 Mar 2026 22:03:02 +0100
Message-Id: <DHD0NQH9UJ21.3J691DBDXS0K0@kernel.org>
To: "Douglas Anderson" <dianders@chromium.org>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH v2] device property: Make modifications of fwnode
 "flags" thread safe
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>, "Rafael J . Wysocki"
 <rafael@kernel.org>, <stable@vger.kernel.org>, "Andy Shevchenko"
 <andriy.shevchenko@linux.intel.com>, "Mark Brown" <broonie@kernel.org>,
 "Wolfram Sang" <wsa+renesas@sang-engineering.com>, "Andrew Lunn"
 <andrew@lunn.ch>, "Daniel Scally" <djrscally@gmail.com>, "David S. Miller"
 <davem@davemloft.net>, "Eric Dumazet" <edumazet@google.com>, "Fabio
 Estevam" <festevam@gmail.com>, "Frank Li" <Frank.Li@nxp.com>, "Heikki
 Krogerus" <heikki.krogerus@linux.intel.com>, "Heiner Kallweit"
 <hkallweit1@gmail.com>, "Jakub Kicinski" <kuba@kernel.org>, "Len Brown"
 <lenb@kernel.org>, "Paolo Abeni" <pabeni@redhat.com>, "Pengutronix Kernel
 Team" <kernel@pengutronix.de>, "Rob Herring" <robh@kernel.org>, "Russell
 King" <linux@armlinux.org.uk>, "Sakari Ailus"
 <sakari.ailus@linux.intel.com>, "Saravana Kannan" <saravanak@kernel.org>,
 "Sascha Hauer" <s.hauer@pengutronix.de>, <devicetree@vger.kernel.org>,
 <driver-core@lists.linux.dev>, <imx@lists.linux.dev>,
 <linux-acpi@vger.kernel.org>, <linux-arm-kernel@lists.infradead.org>,
 <linux-i2c@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
 <linux-spi@vger.kernel.org>, <netdev@vger.kernel.org>
References: <20260317090112.v2.1.I0a4d03104ecd5103df3d76f66c8d21b1d15a2e38@changeid>
In-Reply-To: <20260317090112.v2.1.I0a4d03104ecd5103df3d76f66c8d21b1d15a2e38@changeid>

On Tue Mar 17, 2026 at 5:01 PM CET, Douglas Anderson wrote:
> In various places in the kernel, we modify the fwnode "flags" member
> by doing either:
>   fwnode->flags |=3D SOME_FLAG;
>   fwnode->flags &=3D ~SOME_FLAG;
>
> This type of modification is not thread-safe. If two threads are both
> mucking with the flags at the same time then one can clobber the
> other.
>
> While flags are often modified while under the "fwnode_link_lock",
> this is not universally true.
>
> Create some accessor functions for setting, clearing, and testing the
> FWNODE flags and move all users to these accessor functions. New
> accessor functions use set_bit() and clear_bit(), which are
> thread-safe.
>
> Cc: stable@vger.kernel.org
> Fixes: c2c724c868c4 ("driver core: Add fw_devlink_parse_fwtree()")
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Acked-by: Mark Brown <broonie@kernel.org>
> Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

    [ Fix fwnode_clear_flag() argument alignment, restore dropped blank
      line in fwnode_dev_initialized(), and remove unnecessary parentheses
      around fwnode_test_flag() calls. - Danilo ]

Applied to driver-core-testing, thanks!