[PATCH v3 04/28] driver core: Avoid warning when removing a device while its supplier is unbinding
Rafael J. Wysocki
rafael at kernel.org
Wed Jul 2 11:22:14 PDT 2025
On Fri, Jun 13, 2025 at 3:48 PM Herve Codina <herve.codina at bootlin.com> wrote:
>
> During driver removal, the following warning can appear:
> WARNING: CPU: 1 PID: 139 at drivers/base/core.c:1497 __device_links_no_driver+0xcc/0xfc
> ...
> Call trace:
> __device_links_no_driver+0xcc/0xfc (P)
> device_links_driver_cleanup+0xa8/0xf0
> device_release_driver_internal+0x208/0x23c
> device_links_unbind_consumers+0xe0/0x108
> device_release_driver_internal+0xec/0x23c
> device_links_unbind_consumers+0xe0/0x108
> device_release_driver_internal+0xec/0x23c
> device_links_unbind_consumers+0xe0/0x108
> device_release_driver_internal+0xec/0x23c
> driver_detach+0xa0/0x12c
> bus_remove_driver+0x6c/0xbc
> driver_unregister+0x30/0x60
> pci_unregister_driver+0x20/0x9c
> lan966x_pci_driver_exit+0x18/0xa90 [lan966x_pci]
>
> This warning is triggered when a consumer is removed because the links
> status of its supplier is not DL_DEV_DRIVER_BOUND and the link flag
> DL_FLAG_SYNC_STATE_ONLY is not set.
>
> The topology in terms of consumers/suppliers used was the following
> (consumer ---> supplier):
>
> i2c -----------> OIC ----> PCI device
> | ^
> | |
> +---> pinctrl ---+
>
> When the PCI device is removed, the OIC (interrupt controller) has to be
> removed. In order to remove the OIC, pinctrl and i2c need to be removed
> and to remove pinctrl, i2c need to be removed. The removal order is:
> 1) i2c
> 2) pinctrl
> 3) OIC
> 4) PCI device
>
> In details, the removal sequence is the following (with 0000:01:00.0 the
> PCI device):
> driver_detach: call device_release_driver_internal(0000:01:00.0)...
> device_links_busy(0000:01:00.0):
> links->status = DL_DEV_UNBINDING
> device_links_unbind_consumers(0000:01:00.0):
> 0000:01:00.0--oic link->status = DL_STATE_SUPPLIER_UNBIND
> call device_release_driver_internal(oic)...
> device_links_busy(oic):
> links->status = DL_DEV_UNBINDING
> device_links_unbind_consumers(oic):
> oic--pinctrl link->status = DL_STATE_SUPPLIER_UNBIND
> call device_release_driver_internal(pinctrl)...
> device_links_busy(pinctrl):
> links->status = DL_DEV_UNBINDING
> device_links_unbind_consumers(pinctrl):
> pinctrl--i2c link->status = DL_STATE_SUPPLIER_UNBIND
> call device_release_driver_internal(i2c)...
> device_links_busy(i2c): links->status = DL_DEV_UNBINDING
> __device_links_no_driver(i2c)...
> pinctrl--i2c link->status is DL_STATE_SUPPLIER_UNBIND
> oic--i2c link->status is DL_STATE_ACTIVE
> oic--i2c link->supplier->links.status is DL_DEV_UNBINDING
>
> The warning is triggered by the i2c removal because the OIC (supplier)
> links status is not DL_DEV_DRIVER_BOUND. Its links status is indeed set
> to DL_DEV_UNBINDING.
>
> It is perfectly legit to have the links status set to DL_DEV_UNBINDING
> in that case. Indeed we had started to unbind the OIC which triggered
> the consumer unbinding and didn't finish yet when the i2c is unbound.
>
> Avoid the warning when the supplier links status is set to
> DL_DEV_UNBINDING and thus support this removal sequence without any
> warnings.
>
> Signed-off-by: Herve Codina <herve.codina at bootlin.com>
The change is OK, so
Reviewed-by: Rafael J. Wysocki <rafael at kernel.org>
but it will clash with
https://lore.kernel.org/linux-pm/2793309.mvXUDI8C0e@rjwysocki.net/
that's been queued up by Greg AFAICS.
> ---
> drivers/base/core.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 8fead097c404..ce367c44f642 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -1494,7 +1494,8 @@ static void __device_links_no_driver(struct device *dev)
> if (link->supplier->links.status == DL_DEV_DRIVER_BOUND) {
> WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
> } else {
> - WARN_ON(!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
> + WARN_ON(link->supplier->links.status != DL_DEV_UNBINDING &&
> + !(link->flags & DL_FLAG_SYNC_STATE_ONLY));
> WRITE_ONCE(link->status, DL_STATE_DORMANT);
> }
> }
> --
> 2.49.0
>
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