Re: [PATCH v3 0/5] gpiolib: improve concurrent access to the flags field of struct gpio_desc

[Kent Gibson]

On Tue, Nov 10, 2026 at 02:47:00PM +0100, Bartosz Golaszewski wrote:
> This is a follow-up to our discussion[1] about desc->flags and possible
> races with users who don't/can't synchronize with other means.
> 
> It's an attempt to use try_cmpxchg() to update only the required flags
> atomically where needed + minor fixes using atomic variants of bitops
> where it makes sense.
> 
> [1] https://lore.kernel.org/all/20261015153714.GA105746@rigel/
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
> ---
> Changes in v3:
> - Don't pull in bitops.h when including bitmap.h
> - Improve coding style: fix indentation, set mask later in the function,
>   make lines longer and more readable
> - Use the right Fixes tags
> - Link to v2: https://patch.msgid.link/20261109-gpio-desc-flags-atomic-v2-0-c4c54b476628@xxxxxxxxxxxxxxxx
> 
> Changes in v2:
> - Drop the custom gpiod_update_flags() function and use the existing
>   set_mask_bits() macro instead
> - Add a patch clearing debounce_period_us before GPIOD_FLAG_REQUESTED as
>   suggested by Kent
> - Rename the functions updating flags in gpiolib-cdev.c
> - Don't rename the flags variable
> - Link to v1: https://patch.msgid.link/20261104-gpio-desc-flags-atomic-v1-0-e23cedf619ba@xxxxxxxxxxxxxxxx
> 
> ---
> Bartosz Golaszewski (5):
>       gpiolib: don't overwrite the entire flags field in gpiod_get_direction()
>       gpio: shared: use atomic set_bit() for descriptor flags
>       gpiolib: clear debounce period before the "requested" flag
>       gpiolib: don't overwrite the entire flags field in gpiod_free_commit()
>       gpio: cdev: don't overwrite the whole flags field when configuring lines
> 
>  drivers/gpio/gpiolib-cdev.c   | 93 +++++++++++++++++++++----------------------
>  drivers/gpio/gpiolib-shared.c |  5 +--
>  drivers/gpio/gpiolib.c        | 35 ++++++++--------
>  3 files changed, 65 insertions(+), 68 deletions(-)
> ---
> base-commit: 630059a5a632377b9b7b487baccde92b7ae1dd47
> change-id: 20261104-gpio-desc-flags-atomic-cc963a1ccfd0
> 
> Best regards,
> -- 
> Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
> 

Reviewed-by: Kent Gibson <warthog618@xxxxxxxxx>

Cheers,
Kent.