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Wysocki" , Danilo Krummrich Cc: Douglas Anderson , stable@vger.kernel.org, Andy Shevchenko , Mark Brown , Wolfram Sang , Andrew Lunn , Daniel Scally , "David S. Miller" , Eric Dumazet , Fabio Estevam , Frank Li , Heikki Krogerus , Heiner Kallweit , Jakub Kicinski , Len Brown , Paolo Abeni , Pengutronix Kernel Team , Rob Herring , Russell King , Sakari Ailus , Saravana Kannan , Sascha Hauer , 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 Subject: [PATCH v2] device property: Make modifications of fwnode "flags" thread safe Date: Tue, 17 Mar 2026 09:01:20 -0700 Message-ID: <20260317090112.v2.1.I0a4d03104ecd5103df3d76f66c8d21b1d15a2e38@changeid> X-Mailer: git-send-email 2.53.0.851.ga537e3e6e9-goog Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 Acked-by: Mark Brown Reviewed-by: Wolfram Sang Signed-off-by: Douglas Anderson Reviewed-by: Saravana Kannan --- While this patch is not known for sure to fix any specific issues, it seems possible that it could fix some rare problems. I'm currently trying to track down a hard-to-reproduce heisenbug and one (currently unproven) theory I had was that the fwnode flags could be getting messed up like this. Even if turns out not to fix my heisenbug, though, this seems like a worthwhile change to take. Changes in v2: - Add/use fwnode_assign_flag() (Andy). drivers/base/core.c | 24 +++++++-------- drivers/bus/imx-weim.c | 2 +- drivers/i2c/i2c-core-of.c | 2 +- drivers/net/phy/mdio_bus_provider.c | 4 +-- drivers/of/base.c | 2 +- drivers/of/dynamic.c | 2 +- drivers/of/platform.c | 2 +- drivers/spi/spi.c | 2 +- include/linux/fwnode.h | 45 +++++++++++++++++++++-------- 9 files changed, 53 insertions(+), 32 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 791f9e444df8..f65492a4afc8 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -182,7 +182,7 @@ void fw_devlink_purge_absent_suppliers(struct fwnode_ha= ndle *fwnode) if (fwnode->dev) return; =20 - fwnode->flags |=3D FWNODE_FLAG_NOT_DEVICE; + fwnode_set_flag(fwnode, FWNODE_FLAG_NOT_DEVICE); fwnode_links_purge_consumers(fwnode); =20 fwnode_for_each_available_child_node(fwnode, child) @@ -228,7 +228,7 @@ static void __fw_devlink_pickup_dangling_consumers(stru= ct fwnode_handle *fwnode, if (fwnode->dev && fwnode->dev->bus) return; =20 - fwnode->flags |=3D FWNODE_FLAG_NOT_DEVICE; + fwnode_set_flag(fwnode, FWNODE_FLAG_NOT_DEVICE); __fwnode_links_move_consumers(fwnode, new_sup); =20 fwnode_for_each_available_child_node(fwnode, child) @@ -1012,7 +1012,7 @@ static void device_links_missing_supplier(struct devi= ce *dev) static bool dev_is_best_effort(struct device *dev) { return (fw_devlink_best_effort && dev->can_match) || - (dev->fwnode && (dev->fwnode->flags & FWNODE_FLAG_BEST_EFFORT)); + (dev->fwnode && (fwnode_test_flag(dev->fwnode, FWNODE_FLAG_BEST_EFFORT))= ); } =20 static struct fwnode_handle *fwnode_links_check_suppliers( @@ -1723,11 +1723,11 @@ bool fw_devlink_is_strict(void) =20 static void fw_devlink_parse_fwnode(struct fwnode_handle *fwnode) { - if (fwnode->flags & FWNODE_FLAG_LINKS_ADDED) + if (fwnode_test_flag(fwnode, FWNODE_FLAG_LINKS_ADDED)) return; =20 fwnode_call_int_op(fwnode, add_links); - fwnode->flags |=3D FWNODE_FLAG_LINKS_ADDED; + fwnode_set_flag(fwnode, FWNODE_FLAG_LINKS_ADDED); } =20 static void fw_devlink_parse_fwtree(struct fwnode_handle *fwnode) @@ -1885,7 +1885,7 @@ static bool fwnode_init_without_drv(struct fwnode_han= dle *fwnode) struct device *dev; bool ret; =20 - if (!(fwnode->flags & FWNODE_FLAG_INITIALIZED)) + if (!(fwnode_test_flag(fwnode, FWNODE_FLAG_INITIALIZED))) return false; =20 dev =3D get_dev_from_fwnode(fwnode); @@ -2001,10 +2001,10 @@ static bool __fw_devlink_relax_cycles(struct fwnode= _handle *con_handle, * We aren't trying to find all cycles. Just a cycle between con and * sup_handle. */ - if (sup_handle->flags & FWNODE_FLAG_VISITED) + if (fwnode_test_flag(sup_handle, FWNODE_FLAG_VISITED)) return false; =20 - sup_handle->flags |=3D FWNODE_FLAG_VISITED; + fwnode_set_flag(sup_handle, FWNODE_FLAG_VISITED); =20 /* Termination condition. */ if (sup_handle =3D=3D con_handle) { @@ -2074,7 +2074,7 @@ static bool __fw_devlink_relax_cycles(struct fwnode_h= andle *con_handle, } =20 out: - sup_handle->flags &=3D ~FWNODE_FLAG_VISITED; + fwnode_clear_flag(sup_handle, FWNODE_FLAG_VISITED); put_device(sup_dev); put_device(con_dev); put_device(par_dev); @@ -2127,7 +2127,7 @@ static int fw_devlink_create_devlink(struct device *c= on, * When such a flag is set, we can't create device links where P is the * supplier of C as that would delay the probe of C. */ - if (sup_handle->flags & FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD && + if (fwnode_test_flag(sup_handle, FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD) && fwnode_is_ancestor_of(sup_handle, con->fwnode)) return -EINVAL; =20 @@ -2150,7 +2150,7 @@ static int fw_devlink_create_devlink(struct device *c= on, else flags =3D FW_DEVLINK_FLAGS_PERMISSIVE; =20 - if (sup_handle->flags & FWNODE_FLAG_NOT_DEVICE) + if (fwnode_test_flag(sup_handle, FWNODE_FLAG_NOT_DEVICE)) sup_dev =3D fwnode_get_next_parent_dev(sup_handle); else sup_dev =3D get_dev_from_fwnode(sup_handle); @@ -2162,7 +2162,7 @@ static int fw_devlink_create_devlink(struct device *c= on, * supplier device indefinitely. */ if (sup_dev->links.status =3D=3D DL_DEV_NO_DRIVER && - sup_handle->flags & FWNODE_FLAG_INITIALIZED) { + fwnode_test_flag(sup_handle, FWNODE_FLAG_INITIALIZED)) { dev_dbg(con, "Not linking %pfwf - dev might never probe\n", sup_handle); diff --git a/drivers/bus/imx-weim.c b/drivers/bus/imx-weim.c index 83d623d97f5f..f735e0462c55 100644 --- a/drivers/bus/imx-weim.c +++ b/drivers/bus/imx-weim.c @@ -332,7 +332,7 @@ static int of_weim_notify(struct notifier_block *nb, un= signed long action, * fw_devlink doesn't skip adding consumers to this * device. */ - rd->dn->fwnode.flags &=3D ~FWNODE_FLAG_NOT_DEVICE; + fwnode_clear_flag(&rd->dn->fwnode, FWNODE_FLAG_NOT_DEVICE); if (!of_platform_device_create(rd->dn, NULL, &pdev->dev)) { dev_err(&pdev->dev, "Failed to create child device '%pOF'\n", diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c index eb7fb202355f..354a88d0599e 100644 --- a/drivers/i2c/i2c-core-of.c +++ b/drivers/i2c/i2c-core-of.c @@ -180,7 +180,7 @@ static int of_i2c_notify(struct notifier_block *nb, uns= igned long action, * Clear the flag before adding the device so that fw_devlink * doesn't skip adding consumers to this device. */ - rd->dn->fwnode.flags &=3D ~FWNODE_FLAG_NOT_DEVICE; + fwnode_clear_flag(&rd->dn->fwnode, FWNODE_FLAG_NOT_DEVICE); client =3D of_i2c_register_device(adap, rd->dn); if (IS_ERR(client)) { dev_err(&adap->dev, "failed to create client for '%pOF'\n", diff --git a/drivers/net/phy/mdio_bus_provider.c b/drivers/net/phy/mdio_bus= _provider.c index 4b0637405740..fd691c5424ea 100644 --- a/drivers/net/phy/mdio_bus_provider.c +++ b/drivers/net/phy/mdio_bus_provider.c @@ -294,8 +294,8 @@ int __mdiobus_register(struct mii_bus *bus, struct modu= le *owner) return -EINVAL; =20 if (bus->parent && bus->parent->of_node) - bus->parent->of_node->fwnode.flags |=3D - FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD; + fwnode_set_flag(&bus->parent->of_node->fwnode, + FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD); =20 WARN(bus->state !=3D MDIOBUS_ALLOCATED && bus->state !=3D MDIOBUS_UNREGISTERED, diff --git a/drivers/of/base.c b/drivers/of/base.c index 57420806c1a2..8d1972e18161 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -1915,7 +1915,7 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 a= lign)) if (name) of_stdout =3D of_find_node_opts_by_path(name, &of_stdout_options); if (of_stdout) - of_stdout->fwnode.flags |=3D FWNODE_FLAG_BEST_EFFORT; + fwnode_set_flag(&of_stdout->fwnode, FWNODE_FLAG_BEST_EFFORT); } =20 if (!of_aliases) diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c index 1a06175def37..ade288372101 100644 --- a/drivers/of/dynamic.c +++ b/drivers/of/dynamic.c @@ -225,7 +225,7 @@ static void __of_attach_node(struct device_node *np) np->sibling =3D np->parent->child; np->parent->child =3D np; of_node_clear_flag(np, OF_DETACHED); - np->fwnode.flags |=3D FWNODE_FLAG_NOT_DEVICE; + fwnode_set_flag(&np->fwnode, FWNODE_FLAG_NOT_DEVICE); =20 raw_spin_unlock_irqrestore(&devtree_lock, flags); =20 diff --git a/drivers/of/platform.c b/drivers/of/platform.c index ba591fbceb56..7eeaf8e27b5b 100644 --- a/drivers/of/platform.c +++ b/drivers/of/platform.c @@ -742,7 +742,7 @@ static int of_platform_notify(struct notifier_block *nb, * Clear the flag before adding the device so that fw_devlink * doesn't skip adding consumers to this device. */ - rd->dn->fwnode.flags &=3D ~FWNODE_FLAG_NOT_DEVICE; + fwnode_clear_flag(&rd->dn->fwnode, FWNODE_FLAG_NOT_DEVICE); /* pdev_parent may be NULL when no bus platform device */ pdev_parent =3D of_find_device_by_node(parent); pdev =3D of_platform_device_create(rd->dn, NULL, diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 61f7bde8c7fb..ba8098f1a88c 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -4938,7 +4938,7 @@ static int of_spi_notify(struct notifier_block *nb, u= nsigned long action, * Clear the flag before adding the device so that fw_devlink * doesn't skip adding consumers to this device. */ - rd->dn->fwnode.flags &=3D ~FWNODE_FLAG_NOT_DEVICE; + fwnode_clear_flag(&rd->dn->fwnode, FWNODE_FLAG_NOT_DEVICE); spi =3D of_register_spi_device(ctlr, rd->dn); put_device(&ctlr->dev); =20 diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h index 097be89487bf..c1ebcc6fd896 100644 --- a/include/linux/fwnode.h +++ b/include/linux/fwnode.h @@ -15,6 +15,7 @@ #define _LINUX_FWNODE_H_ =20 #include +#include #include #include #include @@ -42,12 +43,12 @@ struct device; * suppliers. Only enforce ordering with suppliers that have * drivers. */ -#define FWNODE_FLAG_LINKS_ADDED BIT(0) -#define FWNODE_FLAG_NOT_DEVICE BIT(1) -#define FWNODE_FLAG_INITIALIZED BIT(2) -#define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD BIT(3) -#define FWNODE_FLAG_BEST_EFFORT BIT(4) -#define FWNODE_FLAG_VISITED BIT(5) +#define FWNODE_FLAG_LINKS_ADDED 0 +#define FWNODE_FLAG_NOT_DEVICE 1 +#define FWNODE_FLAG_INITIALIZED 2 +#define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD 3 +#define FWNODE_FLAG_BEST_EFFORT 4 +#define FWNODE_FLAG_VISITED 5 =20 struct fwnode_handle { struct fwnode_handle *secondary; @@ -57,7 +58,7 @@ struct fwnode_handle { struct device *dev; struct list_head suppliers; struct list_head consumers; - u8 flags; + unsigned long flags; }; =20 /* @@ -212,16 +213,36 @@ static inline void fwnode_init(struct fwnode_handle *= fwnode, INIT_LIST_HEAD(&fwnode->suppliers); } =20 +static inline void fwnode_set_flag(struct fwnode_handle *fwnode, + unsigned int bit) +{ + set_bit(bit, &fwnode->flags); +} + +static inline void fwnode_clear_flag(struct fwnode_handle *fwnode, + unsigned int bit) +{ + clear_bit(bit, &fwnode->flags); +} + +static inline void fwnode_assign_flag(struct fwnode_handle *fwnode, + unsigned int bit, bool value) +{ + assign_bit(bit, &fwnode->flags, value); +} + +static inline bool fwnode_test_flag(struct fwnode_handle *fwnode, + unsigned int bit) +{ + return test_bit(bit, &fwnode->flags); +} + static inline void fwnode_dev_initialized(struct fwnode_handle *fwnode, bool initialized) { if (IS_ERR_OR_NULL(fwnode)) return; - - if (initialized) - fwnode->flags |=3D FWNODE_FLAG_INITIALIZED; - else - fwnode->flags &=3D ~FWNODE_FLAG_INITIALIZED; + fwnode_assign_flag(fwnode, FWNODE_FLAG_INITIALIZED, initialized); } =20 int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup, --=20 2.53.0.851.ga537e3e6e9-goog