Re: [PATCH 01/22] gpio: protect the list of GPIO devices with SRCU

Bartosz Golaszewski <brgl@xxxxxxxx> · Wed, 31 Jan 2024 13:45:04 +0100

On Wed, Jan 31, 2024 at 10:37 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-20240131]
> [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/20240130124828.14678-2-brgl%40bgdev.pl
> patch subject: [PATCH 01/22] gpio: protect the list of GPIO devices with SRCU
> config: i386-randconfig-141-20240131 (https://download.01.org/0day-ci/archive/20240131/202401311746.be3dlVTg-lkp@xxxxxxxxx/config)
> compiler: clang version 17.0.6 (https://github.com/llvm/llvm-project 6009708b4367171ccdbf4b5905cb6a803753fe18)
>
> 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/202401311746.be3dlVTg-lkp@xxxxxxxxx/
>
> New smatch warnings:
> drivers/gpio/gpiolib.c:4167 gpiod_find_and_request() error: uninitialized symbol 'ret'.
> drivers/gpio/gpiolib.c:4181 gpiod_find_and_request() error: uninitialized symbol 'desc'.
>
> Old smatch warnings:
> drivers/gpio/gpiolib.c:4184 gpiod_find_and_request() error: uninitialized symbol 'desc'.
>
> vim +/ret +4167 drivers/gpio/gpiolib.c
>
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4128
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4129  static struct gpio_desc *gpiod_find_and_request(struct device *consumer,
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4130                                            struct fwnode_handle *fwnode,
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4131                                            const char *con_id,
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4132                                            unsigned int idx,
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4133                                            enum gpiod_flags flags,
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4134                                            const char *label,
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4135                                            bool platform_lookup_allowed)
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4136  {
> ba2dc1cb5491712 Hans de Goede       2022-12-29  4137    unsigned long lookupflags = GPIO_LOOKUP_FLAGS_DEFAULT;
> c122f461ccac0e7 Andy Shevchenko     2023-03-09  4138    struct gpio_desc *desc;
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4139    int ret;
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4140
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4141    scoped_guard(srcu, &gpio_devices_srcu) {
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4142            desc = gpiod_find_by_fwnode(fwnode, consumer, con_id, idx,
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4143                                        &flags, &lookupflags);
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4144            if (gpiod_not_found(desc) && platform_lookup_allowed) {
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4145                    /*
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4146                     * Either we are not using DT or ACPI, or their lookup
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4147                     * did not return a result. In that case, use platform
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4148                     * lookup as a fallback.
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4149                     */
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4150                    dev_dbg(consumer,
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4151                            "using lookup tables for GPIO lookup\n");
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4152                    desc = gpiod_find(consumer, con_id, idx, &lookupflags);
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4153            }
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4154
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4155            if (IS_ERR(desc)) {
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4156                    dev_dbg(consumer, "No GPIO consumer %s found\n",
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4157                            con_id);
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4158                    return desc;
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4159            }
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4160
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4161            /*
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4162             * If a connection label was passed use that, else attempt to use
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4163             * the device name as label
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4164             */
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4165            ret = gpiod_request(desc, label);
> 1fe5210a1bfba00 Bartosz Golaszewski 2024-01-30  4166    }
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11 @4167    if (ret) {
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4168            if (!(ret == -EBUSY && flags & GPIOD_FLAGS_BIT_NONEXCLUSIVE))
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4169                    return ERR_PTR(ret);
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4170
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4171            /*
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4172             * This happens when there are several consumers for
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4173             * the same GPIO line: we just return here without
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4174             * further initialization. It is a bit of a hack.
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4175             * This is necessary to support fixed regulators.
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4176             *
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4177             * FIXME: Make this more sane and safe.
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4178             */
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4179            dev_info(consumer,
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4180                     "nonexclusive access to GPIO for %s\n", con_id);
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11 @4181            return desc;
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4182    }
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4183
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4184    ret = gpiod_configure_flags(desc, con_id, lookupflags, flags);
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4185    if (ret < 0) {
> 8eb1f71e7acca4f Dmitry Torokhov     2022-11-11  4186            dev_dbg(consumer, "setup of GPIO %s failed\n", con_id);
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4187            gpiod_put(desc);
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4188            return ERR_PTR(ret);
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4189    }
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4190
> 9ce4ed5b4db1363 Bartosz Golaszewski 2023-08-21  4191    gpiod_line_state_notify(desc, GPIOLINE_CHANGED_REQUESTED);
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4192
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4193    return desc;
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4194  }
> 0eadd36d9123745 Dmitry Torokhov     2022-09-03  4195
>
> --
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

This is a false-positive coming from the fact the scoped_guard() is
implemented as a for loop. I will initialize the variables anyway to
make smatch happy.

Bart