Re: [PATCH v5] driver core: enforce device_lock for driver_match_device()

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Hi,

Am Dienstag, 20. Januar 2026, 14:22:19 CET schrieb Mark Brown:
> On Wed, Jan 14, 2026 at 12:28:43AM +0800, Gui-Dong Han wrote:
> > Currently, driver_match_device() is called from three sites. One site
> > (__device_attach_driver) holds device_lock(dev), but the other two
> > (bind_store and __driver_attach) do not. This inconsistency means that
> > bus match() callbacks are not guaranteed to be called with the lock
> > held.
> 
> I'm seeing boot hangs on Arm Juno in next/pending-fixes which bisect to
> this commit.  The boot grinds to a halt near the end of boot:
> 
> [    2.570549] ledtrig-cpu: registered to indicate activity on CPUs
> [    2.618301] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
> [    2.623547] msm_serial: driver initialized
> [    2.624058] SuperH (H)SCI(F) driver initialized
> [    2.624312] STM32 USART driver initialized
> 
> with no further output, full log:
> 
>    https://lava.sirena.org.uk/scheduler/job/2387335#L862
> 
> We are also seeing similar looking boot hangs on some Qualcomm platforms
> in Arm's test lab which aren't verified to be the same thing but are
> hanging at a similar point in boot.

I've also experienced a boot problem on an NXP i.MX8QM based board
(DT currently in process of upstreaming). Bisect also resulted in this
commit.

Boot suddenly blocks, after about 4 minutes I get a blocked task backtrace:
[    1.053132] NET: Registered PF_PACKET protocol family
[    1.057958] Key type dns_resolver registered
[    1.070822] registered taskstats version 1
[    1.074738] Loading compiled-in X.509 certificates
[    1.091208] Demotion targets for Node 0: null
[    1.099632] imx-scu system-controller: NXP i.MX SCU Initialized
[  242.855834] INFO: task swapper/0:1 blocked for more than 120 seconds.
[  242.861994]       Not tainted 6.19.0-rc5+ #41
[  242.866304] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  242.874122] task:swapper/0       state:D stack:0     pid:1     tgid:1     ppid:0      task_flags:0x0140 flags:0x00000010
[  242.884981] Call trace:
[  242.887406]  __switch_to+0xdc/0x120 (T)
[  242.891233]  __schedule+0x310/0x7a0
[  242.894708]  schedule+0x30/0xa4
[  242.897835]  schedule_timeout+0x10c/0x118
[  242.901831]  wait_for_completion+0xd4/0x170
[  242.906002]  __flush_work+0x6c/0xdc
[  242.909476]  flush_work+0x2c/0x38
[  242.912777]  deferred_probe_initcall+0x58/0xb0
[  242.917208]  do_one_initcall+0x40/0x24c
[  242.921030]  do_initcalls+0xf0/0x1c4
[  242.924592]  kernel_init_freeable+0x114/0x224
[  242.928936]  kernel_init+0x20/0x1d4
[  242.932413]  ret_from_fork+0x10/0x20
[  242.935990] INFO: task kworker/u16:1:42 blocked for more than 120 seconds.
[  242.942836]       Not tainted 6.19.0-rc5+ #41
[  242.947179] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  242.955000] task:kworker/u16:1   state:D stack:0     pid:42    tgid:42    ppid:2      task_flags:0x4208060 flags:0x00000010
[  242.966127] Workqueue: events_unbound deferred_probe_work_func
[  242.971940] Call trace:
[  242.974364]  __switch_to+0xdc/0x120 (T)
[  242.978195]  __schedule+0x310/0x7a0
[  242.981669]  schedule+0x30/0xa4
[  242.984803]  schedule_preempt_disabled+0x20/0x38
[  242.989401]  __mutex_lock.constprop.0+0x4c4/0xc90
[  242.994094]  __mutex_lock_slowpath+0x10/0x18
[  242.998349]  mutex_lock+0x68/0x74
[  243.001650]  __driver_attach+0x28/0x254
[  243.005473]  bus_for_each_dev+0x74/0xd4
[  243.009295]  driver_attach+0x20/0x28
[  243.012857]  bus_add_driver+0x118/0x238
[  243.016681]  driver_register+0x58/0x114
[  243.020502]  __platform_driver_register+0x20/0x28
[  243.025193]  imx_clk_scu_init+0xe8/0xf8
[  243.029016]  imx8qxp_clk_probe+0x3c/0x11c0
[  243.033099]  platform_probe+0x58/0x90
[  243.036748]  really_probe+0xbc/0x3d4
[  243.040310]  __driver_probe_device+0x7c/0x174
[  243.044653]  driver_probe_device+0x38/0x108
[  243.048823]  __device_attach_driver+0xb0/0x154
[  243.053254]  bus_for_each_drv+0x80/0xdc
[  243.057076]  __device_attach+0x9c/0x1bc
[  243.060899]  device_initial_probe+0x48/0x4c
[  243.065069]  bus_probe_device+0x34/0x98
[  243.068898]  device_add+0x4bc/0x6b4
[  243.072367]  of_device_add+0x40/0x58
[  243.075929]  of_platform_device_create_pdata+0x94/0x158
[  243.081141]  of_platform_bus_create+0xcc/0x280
[  243.085571]  of_platform_populate+0x78/0x174
[  243.089828]  devm_of_platform_populate+0x54/0xb0
[  243.094435]  imx_scu_probe+0x1f8/0x30c
[  243.098169]  platform_probe+0x58/0x90
[  243.101819]  really_probe+0xbc/0x3d4
[  243.105379]  __driver_probe_device+0x7c/0x174
[  243.109728]  driver_probe_device+0x38/0x108
[  243.113896]  __device_attach_driver+0xb0/0x154
[  243.118326]  bus_for_each_drv+0x80/0xdc
[  243.122148]  __device_attach+0x9c/0x1bc
[  243.125971]  device_initial_probe+0x48/0x4c
[  243.130141]  bus_probe_device+0x34/0x98
[  243.133963]  deferred_probe_work_func+0x9c/0xf4
[  243.138480]  process_one_work+0x14c/0x3c0
[  243.142477]  worker_thread+0x2dc/0x3f0
[  243.146212]  kthread+0x124/0x1e4
[  243.149427]  ret_from_fork+0x10/0x20
[  243.152992] INFO: task kworker/u16:1:42 is blocked on a mutex likely owned by task kworker/u16:1:42.

The patches regarding QSPI or SMMU in this thread don't seem to apply for / affect this platform.

Best regards,
Alexander
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