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

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Message-Id: <DFB3BUDFOIN1.3IM5386T534NQ@cknow-tech.com>
Date: Tue, 30 Dec 2025 00:31:17 +0100
From: "Diederik de Haas" <diederik@...ow-tech.com>
To: "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>, "Diederik de
 Haas" <diederik@...ow-tech.com>
Cc: "Michael Wu" <michael@...winnertech.com>, <myungjoo.ham@...sung.com>,
 <cw00.choi@...sung.com>, <linux-kernel@...r.kernel.org>, "Dragan Simic"
 <dsimic@...jaro.org>, <linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH v3] extcon: Fixed sysfs duplicate filename issue

On Sun Dec 28, 2025 at 6:26 PM CET, Andy Shevchenko wrote:
> On Sun, Dec 28, 2025 at 12:01:54PM +0100, Diederik de Haas wrote:
>> On Sat Dec 27, 2025 at 4:08 PM CET, Andy Shevchenko wrote:
>> > On Sun, Dec 21, 2025 at 03:01:11PM +0100, Diederik de Haas wrote:
>> >> 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?
>> >
>> > But have you had a chance to test it? The code looks correct after this patch
>> > as the first we remove the struct device and all associated data (including
>> > sysfs nodes) and then remove the ID from the list. Without that there is a
>> > window to get the same id for the devices that is pending to be removed.
>> 
>> I've build a kernel with it and it will be part of my kernels going
>> forward. But it can take many months before the issue shows up again.
>> So if I don't get it in a year, then I'm going to *assume* it's probably
>> fixed.
>
> I believe you may speed up the test case by creating two shell scripts that
> trying insmod / rmmod the same module in parallel.

I checked on several devices and the phy_rockchip_inno_usb2 module is
used by various other modules on all of them, so I can't just 'rmmod' it.
I guess it should technically be possible to remove all its dependencies
and then remove that module. I don't know if my skills are sufficient
for that and it feels like I'm mostly testing the robustness of the USB
subsystem.

As I regularly already get the following kernel warning
``Warning! ehci_hcd should always be loaded before uhci_hcd and ohci_hcd, not after``
which often results in USB 2 ports not working, I have my doubts about
the robustness anyway.

So I'll just keep an eye out if the ``sysfs: cannot create duplicate
filename`` error pops up again 'naturally' and report if/when it does.

Cheers,
  Diederik