gpio: use srcu_dereference() with SRCU-protected pointers

Lockdep with CONFIG_PROVE_RCU enabled reports false positives about
suspicious rcu_dereference() usage. Let's silence it by using
srcu_dereference() which is the correct helper with SRCU.

Fixes: d83cee3d2bb1 ("gpio: protect the pointer to gpio_chip in gpio_device with SRCU")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202402122234.d85cca9b-lkp@intel.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 6285fa5afbb12c0041714b8510297c11f8ca880a..71ba2a774197b92a7cffab40afc3ec2082ed5bc9 100644 (file)
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -14,6 +14,7 @@
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
+#include <linux/srcu.h>
 #include <linux/sysfs.h>
 #include <linux/types.h>
 
@@ -756,7 +757,7 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
 
        guard(srcu)(&gdev->srcu);
 
-       chip = rcu_dereference(gdev->chip);
+       chip = srcu_dereference(gdev->chip, &gdev->srcu);
        if (!chip)
                return -ENODEV;
 
@@ -800,7 +801,7 @@ void gpiochip_sysfs_unregister(struct gpio_device *gdev)
 
        guard(srcu)(&gdev->srcu);
 
-       chip = rcu_dereference(gdev->chip);
+       chip = srcu_dereference(gdev->chip, &gdev->srcu);
        if (chip)
                return;
 

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 439d32d5aa380697a4c166ac077645f781c9e76f..b095f475805fb91cf1334d985afacf5d757b8f48 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -109,7 +109,7 @@ const char *gpiod_get_label(struct gpio_desc *desc)
                return "interrupt";
 
        return test_bit(FLAG_REQUESTED, &flags) ?
-                       rcu_dereference(desc->label) : NULL;
+                       srcu_dereference(desc->label, &desc->srcu) : NULL;
 }
 
 static int desc_set_label(struct gpio_desc *desc, const char *label)
@@ -447,7 +447,7 @@ static struct gpio_desc *gpio_name_to_desc(const char * const name)
                                 srcu_read_lock_held(&gpio_devices_srcu)) {
                guard(srcu)(&gdev->srcu);
 
-               gc = rcu_dereference(gdev->chip);
+               gc = srcu_dereference(gdev->chip, &gdev->srcu);
                if (!gc)
                        continue;
 
@@ -1190,7 +1190,7 @@ struct gpio_device *gpio_device_find(void *data,
                                 srcu_read_lock_held(&gpio_devices_srcu)) {
                guard(srcu)(&gdev->srcu);
 
-               gc = rcu_dereference(gdev->chip);
+               gc = srcu_dereference(gdev->chip, &gdev->srcu);
 
                if (gc && match(gc, data))
                        return gpio_device_get(gdev);
@@ -2978,7 +2978,7 @@ static int gpiod_get_raw_value_commit(const struct gpio_desc *desc)
 
        guard(srcu)(&gdev->srcu);
 
-       gc = rcu_dereference(gdev->chip);
+       gc = srcu_dereference(gdev->chip, &gdev->srcu);
        if (!gc)
                return -ENODEV;
 
@@ -3012,7 +3012,7 @@ static bool gpio_device_chip_cmp(struct gpio_device *gdev, struct gpio_chip *gc)
 {
        guard(srcu)(&gdev->srcu);
 
-       return gc == rcu_dereference(gdev->chip);
+       return gc == srcu_dereference(gdev->chip, &gdev->srcu);
 }
 
 int gpiod_get_array_value_complex(bool raw, bool can_sleep,
@@ -3593,7 +3593,7 @@ int gpiod_to_irq(const struct gpio_desc *desc)
        gdev = desc->gdev;
        /* FIXME Cannot use gpio_chip_guard due to const desc. */
        guard(srcu)(&gdev->srcu);
-       gc = rcu_dereference(gdev->chip);
+       gc = srcu_dereference(gdev->chip, &gdev->srcu);
        if (!gc)
                return -ENODEV;
 
@@ -4787,7 +4787,7 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev)
 
        guard(srcu)(&gdev->srcu);
 
-       gc = rcu_dereference(gdev->chip);
+       gc = srcu_dereference(gdev->chip, &gdev->srcu);
        if (!gc) {
                seq_puts(s, "Underlying GPIO chip is gone\n");
                return;
@@ -4872,7 +4872,7 @@ static int gpiolib_seq_show(struct seq_file *s, void *v)
 
        guard(srcu)(&gdev->srcu);
 
-       gc = rcu_dereference(gdev->chip);
+       gc = srcu_dereference(gdev->chip, &gdev->srcu);
        if (!gc) {
                seq_printf(s, "%s%s: (dangling chip)",
                           priv->newline ? "\n" : "",

diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 07443d26cbcae895c0f52f19008f3538847d6ec7..ada36aa0f81abdcee6d0dfe7fc99c114726d0640 100644 (file)
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -202,7 +202,8 @@ DEFINE_CLASS(gpio_chip_guard,
 
                _guard.gdev = desc->gdev;
                _guard.idx = srcu_read_lock(&_guard.gdev->srcu);
-               _guard.gc = rcu_dereference(_guard.gdev->chip);
+               _guard.gc = srcu_dereference(_guard.gdev->chip,
+                                            &_guard.gdev->srcu);
 
                _guard;
             }),