Re: [PATCH v3] extcon: Fixed sysfs duplicate filename issue

["Diederik de Haas" <diederik@cknow-tech.com>]

Hi,

On Fri Oct 24, 2025 at 4:49 AM CEST, Michael Wu wrote:
> With current extcon_dev_unregister() timing, ida_free is before
> device_unregister(), that may cause current id re-alloc to another
> device in extcon_dev_register() context but sysfs filename path not
> removal completed yet.

I periodically get errors like this:

[    7.116152] rockchip-usb2phy fe8a0000.usb2phy: error -EEXIST: failed to register extcon device
[    7.117005] rockchip-usb2phy fe8a0000.usb2phy: probe with driver rockchip-usb2phy failed with error -17

This was today on a NanoPi R5S (rk3568), but I have seen it before and
on multiple devices. They are all Rockchip based, but that's (quite)
possible because that's what I use the most (and where I pay quite a bit
of attention to dmesg).

Slightly fuller dmesg output of the above error is here:
https://paste.sr.ht/~diederik/42c6b3405386c823cd9f837d73a9a32e810361be
And via 'journalctl' I hopefully got the full dmesg output:
https://paste.sr.ht/~diederik/7a6109115b1ad85290de482db091dad3759ec159

Here are 2 similar logs, this time on PineTab2 and Quartz64-A (both rk3566)
https://paste.sr.ht/~diederik/cfe606801d3dab0267bea7049687d24c0d6e8d71

Those are all the logs I have saved, but it has happened several times
besides that. But most times I just rebooted and didn't save the log.
Today I looked a bit further, found commit 7bba9e81a6fb, searched on
lore.k.o and found this patch.

So I'm wondering whether this patch would also fix 'my' issue?
Or is this a different issue?

Most of my kernel modules are ``=m`` which is possibly a factor. And
because of that, -EPROBE_DEFER probably happens several times.
Dunno if that's relevant, but figured I'd mention it.

Cheers,
  Diederik

> The right timing shows below:
> on extcon_dev_register: ida_alloc() -> device_register()
> on extcon_dev_unregister: device_unregister() -> ida_free()
>
> stack information when an error occurs:
> sysfs: cannot create duplicate filename '/class/extcon/extcon1'
> Call trace:
>  sysfs_warn_dup+0x68/0x88
>  sysfs_do_create_link_sd+0x94/0xdc
>  sysfs_create_link+0x30/0x48
>  device_add_class_symlinks+0xb4/0x12c
>  device_add+0x1e0/0x48c
>  device_register+0x20/0x34
>  extcon_dev_register+0x3b8/0x5c4
>
> Fixes: 7bba9e81a6fb ("extcon: Use unique number for the extcon device ID")
> Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Michael Wu <michael@allwinnertech.com>
> ---
> ChangeLog:
> V2 -> V3: Dropped some noisy lines in commit messages, suggested by Andy Shevchenko
> V1 -> V2: Update commit msg, suggested by Markus Elfring
> V1: https://lore.kernel.org/all/20251011053719.87055-1-michael@allwinnertech.com/
> ---
> ---
>  drivers/extcon/extcon.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c
> index e7f55c021e562..c08f642d7f5ee 100644
> --- a/drivers/extcon/extcon.c
> +++ b/drivers/extcon/extcon.c
> @@ -1371,10 +1371,10 @@ void extcon_dev_unregister(struct extcon_dev *edev)
>  		return;
>  	}
>  
> -	ida_free(&extcon_dev_ids, edev->id);
> -
>  	device_unregister(&edev->dev);
>  
> +	ida_free(&extcon_dev_ids, edev->id);
> +
>  	if (edev->mutually_exclusive && edev->max_supported) {
>  		for (index = 0; edev->mutually_exclusive[index];
>  				index++)