kernel/linux.git/drivers/base/dd.c, branch v7.2-rc1

driver core: Use system_percpu_wq instead of system_wq

2026-06-02T13:08:56+00:00

Commit 1137838865bf ("driver core: Use mod_delayed_work to prevent lost deferred probe work") added a use of system_wq, which is deprecated in favor of system_percpu_wq added by commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq"). An upcoming warning in the workqueue tree flags this with: workqueue: work func deferred_probe_timeout_work_func enqueued on deprecated workqueue. Use system_{percpu|dfl}_wq instead. Switch to system_percpu_wq to clear up the warning. Fixes: 1137838865bf ("driver core: Use mod_delayed_work to prevent lost deferred probe work") Signed-off-by: Nathan Chancellor Reviewed-by: Rafael J. Wysocki (Intel) Link: https://patch.msgid.link/20260601-driver-core-fix-system_wq-warning-v1-1-f9001a70ee25@kernel.org Signed-off-by: Danilo Krummrich

Merge patch series "rust: device: Higher-Ranked Lifetime Types for device drivers"

2026-05-28T22:38:54+00:00

Danilo Krummrich says: Currently, Rust device drivers access device resources such as PCI BAR mappings and I/O memory regions through Devres. Devres::access() provides zero-overhead access by taking a &Device reference as proof that the device is still bound. Since a &Device is available in almost all contexts by design, Devres is mostly a type-system level proof that the resource is valid, but it can also be used from scopes without this guarantee through its try_access() accessor. This works well in general, but has a few limitations: - Every access to a device resource goes through Devres::access(), which despite zero cost, adds boilerplate to every access site. - Destructors do not receive a &Device, so they must use try_access(), which can fail. In practice the access succeeds if teardown ordering is correct, but the type system can't express this, forcing drivers to handle a failure path that should never be taken. - Sharing a resource across components (e.g. passing a BAR to a sub-component) requires Arc>. - Device references must be stored as ARef rather than plain &Device borrows. These limitations stem from the driver's bus device private data being 'static -- the driver struct cannot borrow from the device reference it receives in probe(), even though it structurally cannot outlive the device binding. This series introduces Higher-Ranked Lifetime Types (HRT) for Rust device drivers. An HRT is a type that is generic over a lifetime -- it does not have a fixed lifetime, but can be instantiated with any lifetime chosen by the caller. Bus driver traits use a Generic Associated Type (GAT) type Data<'bound> to introduce the lifetime on the private data, rather than parameterizing the Driver trait itself. This avoids a driver trait global lifetime and avoids the need for ForLt for bus device private data, making the bus implementations much simpler. ForLt is only needed for auxiliary registration data, where the lifetime is not introduced by a trait callback but must be threaded through Registration. With HRT, driver structs carry a lifetime parameter tied to the device binding scope -- the interval of a bus device being bound to a driver. Device resources like pci::Bar<'bound> and IoMem<'bound> are handed out with this lifetime, so the compiler enforces at build time that they do not escape the binding scope. Before: struct MyDriver { pdev: ARef, bar: Devres>, } let io = self.bar.access(dev)?; io.read32(OFFSET); After: struct MyDriver<'bound> { pdev: &'bound pci::Device, bar: pci::Bar<'bound, BAR_SIZE>, } self.bar.read32(OFFSET); Lifetime-parameterized device resources can be put into a Devres at any point via Bar::into_devres() / IoMem::into_devres(), providing the exact same semantics as before. This is useful for resources shared across subsystem boundaries where revocation is needed. This also synergizes with the upcoming self-referential initialization support in pin-init, which allows one field of the driver struct to borrow another during initialization without unsafe code. The same pattern is applied to auxiliary device registration data as a first example beyond bus device private data. Registration can hold lifetime-parameterized data tied to the parent driver's binding scope. Since the auxiliary bus guarantees that the parent remains bound while the auxiliary device is registered, the registration data can safely borrow the parent's device resources. More generally, binding resource lifetimes to a registration scope applies to every registration that is scoped to a driver binding -- auxiliary devices, class devices, IRQ handlers, workqueues. A follow-up series extends this to class device registrations, starting with DRM, so that class device callbacks (IOCTLs, etc.) can safely access device resources through the separate registration data bound to the registration's lifetime without Devres indirection. Thanks to Gary for coming up with the ForLt implementation; thanks to Alice for the early discussions around lifetime-parameterized private data that helped shape the direction of this work. Link: https://patch.msgid.link/20260525202921.124698-1-dakr@kernel.org Signed-off-by: Danilo Krummrich

rust: driver core: drop drvdata before devres release

2026-05-27T14:22:41+00:00

Move the post_unbind_rust callback before devres_release_all() in device_unbind_cleanup(). With drvdata() removed, the driver's bus device private data is only accessible by the owning driver itself. It is hence safe to drop the driver's bus device private data before devres actions are released. This reordering is the key enabler for Higher-Ranked Lifetime Types (HRT) in Rust device drivers -- it allows driver structs to hold direct references to devres-managed resources, because the bus device private data (and with it all such references) is guaranteed to be dropped while the underlying devres resources are still alive. Without this change, devres resources would be freed first, leaving the driver's bus device private data with dangling references during its destructor. Reviewed-by: Alexandre Courbot Reviewed-by: Gary Guo Reviewed-by: Greg Kroah-Hartman Link: https://patch.msgid.link/20260525202921.124698-6-dakr@kernel.org Signed-off-by: Danilo Krummrich

driver core: Guard deferred probe timeout extension with delayed_work_pending()

2026-05-26T14:51:08+00:00

mod_delayed_work() unconditionally queues the work even when it wasn't previously pending, which can fire the timeout prematurely or restart it after it already fired. Add a delayed_work_pending() guard to restore the originally intended semantics. Premature firing calls fw_devlink_drivers_done() before all built-in drivers have registered, causing fw_devlink to prematurely relax device links for suppliers whose drivers haven't loaded yet. Fixes: 1137838865bf ("driver core: Use mod_delayed_work to prevent lost deferred probe work") Tested-by: Geert Uytterhoeven Reviewed-by: Greg Kroah-Hartman Link: https://patch.msgid.link/20260525012340.3860581-2-dakr@kernel.org Signed-off-by: Danilo Krummrich

driver core: Fix missing jiffies conversion in deferred_probe_extend_timeout()

2026-05-26T14:50:55+00:00

mod_delayed_work() takes jiffies, not seconds. Thus, restore the dropped conversion. While at it, fix incorrect indentation. Fixes: 1137838865bf ("driver core: Use mod_delayed_work to prevent lost deferred probe work") Tested-by: Biju Das Tested-by: Geert Uytterhoeven Reviewed-by: Greg Kroah-Hartman Link: https://patch.msgid.link/20260525012340.3860581-1-dakr@kernel.org Signed-off-by: Danilo Krummrich

driver core: Use mod_delayed_work to prevent lost deferred probe work

2026-05-22T11:33:21+00:00

The deferred_probe_timeout_work may be permanently and unexpectedly canceled when deferred_probe_extend_timeout() executes concurrently. Starting with deferred_probe_timeout_work pending, the problem can occur after the following sequence: CPU0 CPU1 deferred_probe_extend_timeout -> cancel_delayed_work() => true deferred_probe_extend_timeout -> cancel_delayed_work() -> __cancel_work() -> try_grab_pending() -> schedule_delayed_work() -> queue_delayed_work_on() (Since the pending bit is grabbed, it just returns without queuing) -> set_work_pool_and_clear_pending() (This __cancel_work() returns false and the work will never be queued again) The root cause is that the WORK_STRUCT_PENDING_BIT of the work_struct is set temporarily in __cancel_work() (via try_grab_pending()). This transient state prevents the work_struct from being successfully queued by another CPU. To fix this, replace the original non-atomic cancel and schedule mechanism with mod_delayed_work(). This ensures the modification is handled atomically and guarantees that the work is not lost. Fixes: 2b28a1a84a0e ("driver core: Extend deferred probe timeout on driver registration") Signed-off-by: Zhang Yuwei Link: https://patch.msgid.link/20260410024448.387231-1-zhangyuwei20@huawei.com Signed-off-by: Greg Kroah-Hartman

driver core: Replace dev->state_synced with dev_state_synced()

2026-04-26T21:43:31+00:00

In C, bitfields are not necessarily safe to modify from multiple threads without locking. Switch "state_synced" over to the "flags" field so modifications are safe. Cc: Saravana Kannan Reviewed-by: Rafael J. Wysocki (Intel) Reviewed-by: Danilo Krummrich Acked-by: Greg Kroah-Hartman Acked-by: Marek Szyprowski Signed-off-by: Douglas Anderson Link: https://patch.msgid.link/20260406162231.v5.6.Idb4818e1159fef104c7756bfd6e7ba8f374bebcd@changeid Signed-off-by: Danilo Krummrich

driver core: Replace dev->can_match with dev_can_match()

2026-04-26T21:38:02+00:00

In C, bitfields are not necessarily safe to modify from multiple threads without locking. Switch "can_match" over to the "flags" field so modifications are safe. Cc: Saravana Kannan Reviewed-by: Rafael J. Wysocki (Intel) Reviewed-by: Danilo Krummrich Acked-by: Greg Kroah-Hartman Acked-by: Marek Szyprowski Signed-off-by: Douglas Anderson Link: https://patch.msgid.link/20260406162231.v5.2.I54b3ae6311ff34ad30227659d91bb109911a4aea@changeid Signed-off-by: Danilo Krummrich

Merge tag 'driver-core-7.1-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core

2026-04-19T19:58:08+00:00

Pull driver core fixes from Danilo Krummrich: - Prevent a device from being probed before device_add() has finished initializing it; gate probe with a "ready_to_probe" device flag to avoid races with concurrent driver_register() calls - Fix a kernel-doc warning for DEV_FLAG_COUNT introduced by the above - Return -ENOTCONN from software_node_get_reference_args() when a referenced software node is known but not yet registered, allowing callers to defer probe - In sysfs_group_attrs_change_owner(), also check is_visible_const(); missed when the const variant was introduced * tag 'driver-core-7.1-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core: driver core: Add kernel-doc for DEV_FLAG_COUNT enum value sysfs: attribute_group: Respect is_visible_const() when changing owner software node: return -ENOTCONN when referenced swnode is not registered yet driver core: Don't let a device probe until it's ready

driver core: Don't let a device probe until it's ready

2026-04-11T12:32:07+00:00

The moment we link a "struct device" into the list of devices for the bus, it's possible probe can happen. This is because another thread can load the driver at any time and that can cause the device to probe. This has been seen in practice with a stack crawl that looks like this [1]: really_probe() __driver_probe_device() driver_probe_device() __driver_attach() bus_for_each_dev() driver_attach() bus_add_driver() driver_register() __platform_driver_register() init_module() [some module] do_one_initcall() do_init_module() load_module() __arm64_sys_finit_module() invoke_syscall() As a result of the above, it was seen that device_links_driver_bound() could be called for the device before "dev->fwnode->dev" was assigned. This prevented __fw_devlink_pickup_dangling_consumers() from being called which meant that other devices waiting on our driver's sub-nodes were stuck deferring forever. It's believed that this problem is showing up suddenly for two reasons: 1. Android has recently (last ~1 year) implemented an optimization to the order it loads modules [2]. When devices opt-in to this faster loading, modules are loaded one-after-the-other very quickly. This is unlike how other distributions do it. The reproduction of this problem has only been seen on devices that opt-in to Android's "parallel module loading". 2. Android devices typically opt-in to fw_devlink, and the most noticeable issue is the NULL "dev->fwnode->dev" in device_links_driver_bound(). fw_devlink is somewhat new code and also not in use by all Linux devices. Even though the specific symptom where "dev->fwnode->dev" wasn't assigned could be fixed by moving that assignment higher in device_add(), other parts of device_add() (like the call to device_pm_add()) are also important to run before probe. Only moving the "dev->fwnode->dev" assignment would likely fix the current symptoms but lead to difficult-to-debug problems in the future. Fix the problem by preventing probe until device_add() has run far enough that the device is ready to probe. If somehow we end up trying to probe before we're allowed, __driver_probe_device() will return -EPROBE_DEFER which will make certain the device is noticed. In the race condition that was seen with Android's faster module loading, we will temporarily add the device to the deferred list and then take it off immediately when device_add() probes the device. Instead of adding another flag to the bitfields already in "struct device", instead add a new "flags" field and use that. This allows us to freely change the bit from different thread without worrying about corrupting nearby bits (and means threads changing other bit won't corrupt us). [1] Captured on a machine running a downstream 6.6 kernel [2] https://cs.android.com/android/platform/superproject/main/+/main:system/core/libmodprobe/libmodprobe.cpp?q=LoadModulesParallel Cc: stable@vger.kernel.org Fixes: 2023c610dc54 ("Driver core: add new device to bus's list before probing") Reviewed-by: Alan Stern Reviewed-by: Rafael J. Wysocki (Intel) Reviewed-by: Danilo Krummrich Acked-by: Greg Kroah-Hartman Acked-by: Marek Szyprowski Signed-off-by: Douglas Anderson Link: https://patch.msgid.link/20260406162231.v5.1.Id750b0fbcc94f23ed04b7aecabcead688d0d8c17@changeid Signed-off-by: Danilo Krummrich