Re: [PATCH] gpiolib: acpi: Move storage of acpi_gpio_chip

[Hamish Martin <Hamish.Martin@xxxxxxxxxxxxxxxxxxx>]

On Thu, 2024-03-14 at 15:18 +0200, andriy.shevchenko@xxxxxxxxxxxxxxx
wrote:
> On Thu, Mar 14, 2024 at 01:13:31AM +0000, Hamish Martin wrote:
> > On Wed, 2024-03-13 at 13:26 +0200, Andy Shevchenko wrote:
> 
> ...
> 
> > Removing the setting of the handle to invalid may be the right fix
> > but
> > I don't feel I know the code well enough to make a decision on
> > that. It
> > certainly doesn't resolve things immediately - I saw ref counting
> > warnings output.
> 
> Not removing, but moving to the better place?
> Can you share warnings, though?
> 
For context here is the current call chain that leads to
acpi_gpiochip_remove():

 acpi_gpiochip_remove+0x32/0x1a0
 gpiochip_remove+0x39/0x140
 devres_release_group+0xe6/0x160
 i2c_device_remove+0x2d/0x80
 device_release_driver_internal+0x19a/0x200
 bus_remove_device+0xbf/0x100
 device_del+0x157/0x490
 ? __pfx_device_match_fwnode+0x10/0x10
 ? srso_return_thunk+0x5/0x5f
 device_unregister+0xd/0x30
 i2c_acpi_notify+0x10e/0x160
 notifier_call_chain+0x58/0xd0
 blocking_notifier_call_chain+0x3a/0x60
 acpi_device_del_work_fn+0x85/0x1d0
 process_one_work+0x134/0x2f0
 worker_thread+0x2f0/0x410
 ? __pfx_worker_thread+0x10/0x10
 kthread+0xe3/0x110
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x2f/0x50
 ? __pfx_kthread+0x10/0x10
 ret_from_fork_asm+0x1b/0x30

I removed the setting of adev->handle = INVALID_ACPI_HANDLE from
acpi_scan_drop_device() and shifted it to just after the call to
blocking_notifier_call_chain() in acpi_device_del_work_fn().
With that it seems things progress further with the call to
acpi_get_data() in acpi_gpiochip_remove() succeeding now. However,
later in acpi_gpiochip_free_regions() we hit this error:

pca953x i2c-PRP0001:03: Failed to remove GPIO OpRegion handler

We also get these errors:
ACPI Warning: Obj 00000000ba6a9600, Reference Count is already zero,
cannot decrement
 (20230628/utdelete-422)

> P.S.
> I'm not an expert in ACPICA and low lever of ACPI glue layer in the
> Linux
> kernel, perhaps Rafael can suggest something better.
> 
OK, thanks for your help. Hopefully Rafael can add something to the
discssion.

Thanks,
Hamish M