linux-stable.git/drivers/base/dd.c, branch linux-rolling-stable

driver core: Use system_percpu_wq instead of system_wq

2026-07-24T14:19:29+00:00

[ Upstream commit fda8355f13ea3c0f9499acdeff3024995b474948 ]

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 
Signed-off-by: Sasha Levin

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

2026-07-24T14:19:20+00:00

[ Upstream commit 557495bc879013c3d5e21d667e987e7ce3a514de ]

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 
Signed-off-by: Sasha Levin

driver core: Fix missing jiffies conversion in deferred_probe_extend_timeout()

2026-07-24T14:19:20+00:00

[ Upstream commit f9e6da99fe49277979798a1c3b9790ae10aaa18a ]

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 
Signed-off-by: Sasha Levin

driver core: Use mod_delayed_work to prevent lost deferred probe work

2026-07-24T14:19:18+00:00

[ Upstream commit 1137838865bfc9a7cd5869c1dc5c22aa45ec12c8 ]

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 
Signed-off-by: Sasha Levin

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

driver core: Make deferred_probe_timeout default a Kconfig option

2026-03-30T18:45:27+00:00

Code using driver_deferred_probe_check_state() differs from most
EPROBE_DEFER handling in the kernel. Where other EPROBE_DEFER handling
(e.g. clks, gpios and regulators) waits indefinitely for suppliers to
show up, code using driver_deferred_probe_check_state() will fail
after the deferred_probe_timeout.

This is a problem for generic distro kernels which want to support many
boards using a single kernel build. These kernels want as much drivers to
be modular as possible. The initrd also should be as small as possible,
so the initrd will *not* have drivers not needing to get the rootfs.

Combine this with waiting for a full-disk encryption password in
the initrd and it is pretty much guaranteed that the default 10s timeout
will be hit, causing probe() failures when drivers on the rootfs happen
to get modprobe-d before other rootfs modules providing their suppliers.

Make the default timeout configurable from Kconfig to allow distro kernel
configs where many of the supplier drivers are modules to set the default
through Kconfig.

Reviewed-by: Saravana Kannan 
Signed-off-by: Hans de Goede 
Link: https://patch.msgid.link/20260314084916.10868-1-johannes.goede@oss.qualcomm.com
[ Drop deferred_probe_timeout documentation change in
  kernel-parameters.txt. - Danilo ]
Signed-off-by: Danilo Krummrich

driver core: simplify __device_set_driver_override() clearing logic

2026-03-30T12:45:51+00:00

Currently, __device_set_driver_override() handles clearing the override
via empty string ("") and newline ("\n") in two separate paths. The "\n"
case also performs an unnecessary memory allocation and immediate free.

Simplify the logic by initializing 'new' to NULL and only allocating
memory if the string length remains non-zero after stripping the
trailing newline.

Reduce code size, improve readability, and avoid unnecessary memory
operations.

No functional change intended.

Suggested-by: Geert Uytterhoeven 
Link: https://lore.kernel.org/driver-core/DGS82WWLXPJ0.2EH4VJSF30UR5@kernel.org/
Signed-off-by: Gui-Dong Han 
Link: https://patch.msgid.link/20260325090905.169000-1-hanguidong02@gmail.com
[ Narrow cp's scope to the newline handling block; use scoped_guard().
  - Danilo ]
Signed-off-by: Danilo Krummrich

driver core: generalize driver_override in struct device

2026-03-17T19:30:23+00:00

Currently, there are 12 busses (including platform and PCI) that
duplicate the driver_override logic for their individual devices.

All of them seem to be prone to the bug described in [1].

While this could be solved for every bus individually using a separate
lock, solving this in the driver-core generically results in less (and
cleaner) changes overall.

Thus, move driver_override to struct device, provide corresponding
accessors for busses and handle locking with a separate lock internally.

In particular, add device_set_driver_override(),
device_has_driver_override(), device_match_driver_override() and
generalize the sysfs store() and show() callbacks via a driver_override
feature flag in struct bus_type.

Until all busses have migrated, keep driver_set_override() in place.

Note that we can't use the device lock for the reasons described in [2].

Link: https://bugzilla.kernel.org/show_bug.cgi?id=220789 [1]
Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [2]
Tested-by: Gui-Dong Han 
Co-developed-by: Gui-Dong Han 
Signed-off-by: Gui-Dong Han 
Reviewed-by: Greg Kroah-Hartman 
Link: https://patch.msgid.link/20260303115720.48783-2-dakr@kernel.org
[ Use dev->bus instead of sp->bus for consistency; fix commit message to
  refer to the struct bus_type's driver_override feature flag. - Danilo ]
Signed-off-by: Danilo Krummrich

Revert "driver core: enforce device_lock for driver_match_device()"

2026-03-03T12:12:42+00:00

This reverts commit dc23806a7c47 ("driver core: enforce device_lock for
driver_match_device()") and commit 289b14592cef ("driver core: fix
inverted "locked" suffix of driver_match_device()").

While technically correct, there is a major downside to this approach:

When a device is already present in the system and a driver is
registered on the same bus, we iterate over all devices registered on
this bus to see if one of them matches. If we come across an already
bound one where the corresponding driver crashed while holding the
device lock (e.g. in probe()) we can't make any progress anymore.

However, drivers are typically the least tested code in the kernel and
hence it is a case that is likely to happen regularly. Besides hurting
developer ergonomics, it potentially decreases chances of shutting
things down cleanly and obtaining logs in production environments as
well [1].

This came up in the context of a firewire bug, which only in combination
with the reverted commit, caused the machine to hang [2]. Additionally,
it was observed in [3].

Thus, revert commit dc23806a7c47 ("driver core: enforce device_lock for
driver_match_device()") and add a brief note clarifying that an
implementer of struct bus_type must not expect match() to be called with
the device lock held.

Link: https://lore.kernel.org/driver-core/DGRGTIRHA62X.3RY09D9SOK77P@kernel.org/ [1]
Link: https://lore.kernel.org/all/67f655bb-4d81-4609-b008-68d200255dd2@davidgow.net/ [2]
Link: https://lore.kernel.org/lkml/CALbr=LZ4v7N=tO1vgOsyj9AS+XuNbn6kG-QcF+PacdMjSo0iyw@mail.gmail.com/ [3]
Reported-by: Linus Torvalds 
Closes: https://lore.kernel.org/driver-core/CAHk-=wgJ_L1C=HjcYJotg_zrZEmiLFJaoic+PWthjuQrutrfJw@mail.gmail.com/
Reviewed-by: Gui-Dong Han 
Acked-by: Greg Kroah-Hartman 
Link: https://patch.msgid.link/20260302002545.19389-1-dakr@kernel.org
[ Add additional Link: reference. - Danilo ]
Signed-off-by: Danilo Krummrich