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Tue, 07 May 2024 10:24:21 -0700 (PDT) From: Bartosz Golaszewski To: Kent Gibson , Linus Walleij Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski , "Paul E . McKenney" Subject: [PATCH] gpiolib: use a single SRCU struct for all GPIO descriptors Date: Tue, 7 May 2024 19:24:14 +0200 Message-Id: <20240507172414.28513-1-brgl@bgdev.pl> X-Mailer: git-send-email 2.40.1 Precedence: bulk X-Mailing-List: linux-gpio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Bartosz Golaszewski We used a per-descriptor SRCU struct in order to not impose a wait with synchronize_srcu() for descriptor X on read-only operations of descriptor Y. Now that we no longer call synchronize_srcu() on descriptor label change but only when releasing descriptor resources, we can use a single SRCU structure for all GPIO descriptors in a given chip. Suggested-by: Paul E. McKenney Signed-off-by: Bartosz Golaszewski Acked-by: Paul E. McKenney --- drivers/gpio/gpiolib-cdev.c | 2 +- drivers/gpio/gpiolib.c | 41 +++++++++++++++++-------------------- drivers/gpio/gpiolib.h | 10 ++++----- 3 files changed, 25 insertions(+), 28 deletions(-) diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c index d09c7d728365..fea149ae7774 100644 --- a/drivers/gpio/gpiolib-cdev.c +++ b/drivers/gpio/gpiolib-cdev.c @@ -2351,7 +2351,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc, dflags = READ_ONCE(desc->flags); - scoped_guard(srcu, &desc->srcu) { + scoped_guard(srcu, &desc->gdev->desc_srcu) { label = gpiod_get_label(desc); if (label && test_bit(FLAG_REQUESTED, &dflags)) strscpy(info->consumer, label, diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 2fa3756c9073..fa50db0c3605 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -112,8 +112,8 @@ const char *gpiod_get_label(struct gpio_desc *desc) if (!test_bit(FLAG_REQUESTED, &flags)) return NULL; - label = srcu_dereference_check(desc->label, &desc->srcu, - srcu_read_lock_held(&desc->srcu)); + label = srcu_dereference_check(desc->label, &desc->gdev->desc_srcu, + srcu_read_lock_held(&desc->gdev->desc_srcu)); return label->str; } @@ -138,7 +138,7 @@ static int desc_set_label(struct gpio_desc *desc, const char *label) old = rcu_replace_pointer(desc->label, new, 1); if (old) - call_srcu(&desc->srcu, &old->rh, desc_free_label); + call_srcu(&desc->gdev->desc_srcu, &old->rh, desc_free_label); return 0; } @@ -709,13 +709,10 @@ EXPORT_SYMBOL_GPL(gpiochip_line_is_valid); static void gpiodev_release(struct device *dev) { struct gpio_device *gdev = to_gpio_device(dev); - unsigned int i; - for (i = 0; i < gdev->ngpio; i++) { - /* Free pending label. */ - synchronize_srcu(&gdev->descs[i].srcu); - cleanup_srcu_struct(&gdev->descs[i].srcu); - } + /* Call pending kfree()s for descriptor labels. */ + synchronize_srcu(&gdev->desc_srcu); + cleanup_srcu_struct(&gdev->desc_srcu); ida_free(&gpio_ida, gdev->id); kfree_const(gdev->label); @@ -992,6 +989,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data, if (ret) goto err_remove_from_list; + ret = init_srcu_struct(&gdev->desc_srcu); + if (ret) + goto err_cleanup_gdev_srcu; + #ifdef CONFIG_PINCTRL INIT_LIST_HEAD(&gdev->pin_ranges); #endif @@ -999,23 +1000,19 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data, if (gc->names) { ret = gpiochip_set_desc_names(gc); if (ret) - goto err_cleanup_gdev_srcu; + goto err_cleanup_desc_srcu; } ret = gpiochip_set_names(gc); if (ret) - goto err_cleanup_gdev_srcu; + goto err_cleanup_desc_srcu; ret = gpiochip_init_valid_mask(gc); if (ret) - goto err_cleanup_gdev_srcu; + goto err_cleanup_desc_srcu; for (desc_index = 0; desc_index < gc->ngpio; desc_index++) { struct gpio_desc *desc = &gdev->descs[desc_index]; - ret = init_srcu_struct(&desc->srcu); - if (ret) - goto err_cleanup_desc_srcu; - if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index)) { assign_bit(FLAG_IS_OUT, &desc->flags, !gc->get_direction(gc, desc_index)); @@ -1027,7 +1024,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data, ret = of_gpiochip_add(gc); if (ret) - goto err_cleanup_desc_srcu; + goto err_free_valid_mask; ret = gpiochip_add_pin_ranges(gc); if (ret) @@ -1074,10 +1071,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data, gpiochip_remove_pin_ranges(gc); err_remove_of_chip: of_gpiochip_remove(gc); -err_cleanup_desc_srcu: - while (desc_index--) - cleanup_srcu_struct(&gdev->descs[desc_index].srcu); +err_free_valid_mask: gpiochip_free_valid_mask(gc); +err_cleanup_desc_srcu: + cleanup_srcu_struct(&gdev->desc_srcu); err_cleanup_gdev_srcu: cleanup_srcu_struct(&gdev->srcu); err_remove_from_list: @@ -2407,7 +2404,7 @@ char *gpiochip_dup_line_label(struct gpio_chip *gc, unsigned int offset) if (!test_bit(FLAG_REQUESTED, &desc->flags)) return NULL; - guard(srcu)(&desc->srcu); + guard(srcu)(&desc->gdev->desc_srcu); label = kstrdup(gpiod_get_label(desc), GFP_KERNEL); if (!label) @@ -4798,7 +4795,7 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev) } for_each_gpio_desc(gc, desc) { - guard(srcu)(&desc->srcu); + guard(srcu)(&desc->gdev->desc_srcu); if (test_bit(FLAG_REQUESTED, &desc->flags)) { gpiod_get_direction(desc); is_out = test_bit(FLAG_IS_OUT, &desc->flags); diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h index 69a353c789f0..8e0e211ebf08 100644 --- a/drivers/gpio/gpiolib.h +++ b/drivers/gpio/gpiolib.h @@ -31,6 +31,7 @@ * @chip: pointer to the corresponding gpiochip, holding static * data for this device * @descs: array of ngpio descriptors. + * @desc_srcu: ensures consistent state of GPIO descriptors exposed to users * @ngpio: the number of GPIO lines on this GPIO device, equal to the size * of the @descs array. * @can_sleep: indicate whether the GPIO chip driver's callbacks can sleep @@ -61,6 +62,7 @@ struct gpio_device { struct module *owner; struct gpio_chip __rcu *chip; struct gpio_desc *descs; + struct srcu_struct desc_srcu; int base; u16 ngpio; bool can_sleep; @@ -150,7 +152,6 @@ struct gpio_desc_label { * @label: Name of the consumer * @name: Line name * @hog: Pointer to the device node that hogs this line (if any) - * @srcu: SRCU struct protecting the label pointer. * * These are obtained using gpiod_get() and are preferable to the old * integer-based handles. @@ -188,7 +189,6 @@ struct gpio_desc { #ifdef CONFIG_OF_DYNAMIC struct device_node *hog; #endif - struct srcu_struct srcu; }; #define gpiod_not_found(desc) (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT) @@ -256,7 +256,7 @@ static inline int gpio_chip_hwgpio(const struct gpio_desc *desc) #define gpiod_err(desc, fmt, ...) \ do { \ - scoped_guard(srcu, &desc->srcu) { \ + scoped_guard(srcu, &desc->gdev->desc_srcu) { \ pr_err("gpio-%d (%s): " fmt, desc_to_gpio(desc), \ gpiod_get_label(desc) ? : "?", ##__VA_ARGS__); \ } \ @@ -264,7 +264,7 @@ do { \ #define gpiod_warn(desc, fmt, ...) \ do { \ - scoped_guard(srcu, &desc->srcu) { \ + scoped_guard(srcu, &desc->gdev->desc_srcu) { \ pr_warn("gpio-%d (%s): " fmt, desc_to_gpio(desc), \ gpiod_get_label(desc) ? : "?", ##__VA_ARGS__); \ } \ @@ -272,7 +272,7 @@ do { \ #define gpiod_dbg(desc, fmt, ...) \ do { \ - scoped_guard(srcu, &desc->srcu) { \ + scoped_guard(srcu, &desc->gdev->desc_srcu) { \ pr_debug("gpio-%d (%s): " fmt, desc_to_gpio(desc), \ gpiod_get_label(desc) ? : "?", ##__VA_ARGS__); \ } \