Re: [PATCH 20/22] gpio: protect the pointer to gpio_chip in gpio_device with SRCU

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Wed, Jan 31, 2024 at 3:21 AM kernel test robot <lkp@xxxxxxxxx> wrote:
>
> Hi Bartosz,
>
> kernel test robot noticed the following build warnings:
>
> [auto build test WARNING on brgl/gpio/for-next]
> [also build test WARNING on linus/master v6.8-rc2 next-20240130]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
> url:    https://github.com/intel-lab-lkp/linux/commits/Bartosz-Golaszewski/gpio-protect-the-list-of-GPIO-devices-with-SRCU/20240130-205537
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux.git gpio/for-next
> patch link:    https://lore.kernel.org/r/20240130124828.14678-21-brgl%40bgdev.pl
> patch subject: [PATCH 20/22] gpio: protect the pointer to gpio_chip in gpio_device with SRCU
> config: x86_64-randconfig-122-20240131 (https://download.01.org/0day-ci/archive/20240131/202401311050.YNdm98Hv-lkp@xxxxxxxxx/config)
> compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240131/202401311050.YNdm98Hv-lkp@xxxxxxxxx/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202401311050.YNdm98Hv-lkp@xxxxxxxxx/
>
> sparse warnings: (new ones prefixed by >>)
> >> drivers/gpio/gpiolib.c:444:22: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.c:444:22: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.c:444:22: sparse:    struct gpio_chip *
>    drivers/gpio/gpiolib.c:1103:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.c:1103:9: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.c:1103:9: sparse:    struct gpio_chip *
>    drivers/gpio/gpiolib.c:1182:22: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.c:1182:22: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.c:1182:22: sparse:    struct gpio_chip *
>    drivers/gpio/gpiolib.c:2970:14: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.c:2970:14: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.c:2970:14: sparse:    struct gpio_chip *
>    drivers/gpio/gpiolib.c:3004:22: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.c:3004:22: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.c:3004:22: sparse:    struct gpio_chip *
>    drivers/gpio/gpiolib.c:3585:14: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.c:3585:14: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.c:3585:14: sparse:    struct gpio_chip *
>    drivers/gpio/gpiolib.c:4772:14: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.c:4772:14: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.c:4772:14: sparse:    struct gpio_chip *
>    drivers/gpio/gpiolib.c:4846:14: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.c:4846:14: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.c:4846:14: sparse:    struct gpio_chip *
>    drivers/gpio/gpiolib.c: note: in included file:
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
> >> drivers/gpio/gpiolib.h:202:1: sparse: sparse: incompatible types in comparison expression (different address spaces):
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip [noderef] __rcu *
>    drivers/gpio/gpiolib.h:202:1: sparse:    struct gpio_chip *
>
> vim +444 drivers/gpio/gpiolib.c
>
>    422
>    423  /*
>    424   * Convert a GPIO name to its descriptor
>    425   * Note that there is no guarantee that GPIO names are globally unique!
>    426   * Hence this function will return, if it exists, a reference to the first GPIO
>    427   * line found that matches the given name.
>    428   */
>    429  static struct gpio_desc *gpio_name_to_desc(const char * const name)
>    430  {
>    431          struct gpio_device *gdev;
>    432          struct gpio_desc *desc;
>    433          struct gpio_chip *gc;
>    434
>    435          if (!name)
>    436                  return NULL;
>    437
>    438          guard(srcu)(&gpio_devices_srcu);
>    439
>    440          list_for_each_entry_srcu(gdev, &gpio_devices, list,
>    441                                   srcu_read_lock_held(&gpio_devices_srcu)) {
>    442                  guard(srcu)(&gdev->srcu);
>    443
>  > 444                  gc = rcu_dereference(gdev->chip);
>    445                  if (!gc)
>    446                          continue;
>    447
>    448                  for_each_gpio_desc(gc, desc) {
>    449                          if (desc->name && !strcmp(desc->name, name))
>    450                                  return desc;
>    451                  }
>    452          }
>    453
>    454          return NULL;
>    455  }
>    456
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

Paul,

Should I care about these warnings? They seem to be emitted for a lot
of RCU code already upstream. I'm not even sure how I'd go about
addressing them honestly.

Bart