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gpiolib: replace the GPIO device mutex with a read-write semaphore

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There are only two spots where we modify (add to or remove objects from)
the GPIO device list. Readers should be able to access it concurrently.
Replace the mutex with a read-write semaphore and adjust the locking
operations accordingly.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Bartosz Golaszewski 2024-01-02 16:59:48 +01:00
parent 48e1b4d369
commit 1979a28075
3 changed files with 11 additions and 11 deletions
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2
drivers/gpio/gpiolib-sysfs.c
View file

@ -773,7 +773,7 @@ int gpiochip_sysfs_register_all(void)
struct gpio_device *gdev;
int ret;
guard(mutex)(&gpio_devices_lock);
guard(rwsem_read)(&gpio_devices_sem);
list_for_each_entry(gdev, &gpio_devices, list) {
if (gdev->mockdev)

18
drivers/gpio/gpiolib.c
View file

@ -85,7 +85,7 @@ static DEFINE_MUTEX(gpio_lookup_lock);
static LIST_HEAD(gpio_lookup_list);
LIST_HEAD(gpio_devices);
DEFINE_MUTEX(gpio_devices_lock);
DECLARE_RWSEM(gpio_devices_sem);
static DEFINE_MUTEX(gpio_machine_hogs_mutex);
static LIST_HEAD(gpio_machine_hogs);
@ -118,7 +118,7 @@ struct gpio_desc *gpio_to_desc(unsigned gpio)
{
struct gpio_device *gdev;
scoped_guard(mutex, &gpio_devices_lock) {
scoped_guard(rwsem_read, &gpio_devices_sem) {
list_for_each_entry(gdev, &gpio_devices, list) {
if (gdev->base <= gpio &&
gdev->base + gdev->ngpio > gpio)
@ -402,7 +402,7 @@ static struct gpio_desc *gpio_name_to_desc(const char * const name)
if (!name)
return NULL;
guard(mutex)(&gpio_devices_lock);
guard(rwsem_read)(&gpio_devices_sem);
list_for_each_entry(gdev, &gpio_devices, list) {
struct gpio_desc *desc;
@ -871,7 +871,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
gdev->ngpio = gc->ngpio;
scoped_guard(mutex, &gpio_devices_lock) {
scoped_guard(rwsem_write, &gpio_devices_sem) {
/*
* TODO: this allocates a Linux GPIO number base in the global
* GPIO numberspace for this chip. In the long run we want to
@ -1001,7 +1001,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
goto err_print_message;
}
err_remove_from_list:
scoped_guard(mutex, &gpio_devices_lock)
scoped_guard(rwsem_write, &gpio_devices_sem)
list_del(&gdev->list);
err_free_label:
kfree_const(gdev->label);
@ -1065,7 +1065,7 @@ void gpiochip_remove(struct gpio_chip *gc)
dev_crit(&gdev->dev,
"REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n");
scoped_guard(mutex, &gpio_devices_lock)
scoped_guard(rwsem_write, &gpio_devices_sem)
list_del(&gdev->list);
/*
@ -1114,7 +1114,7 @@ struct gpio_device *gpio_device_find(void *data,
*/
might_sleep();
guard(mutex)(&gpio_devices_lock);
guard(rwsem_read)(&gpio_devices_sem);
list_for_each_entry(gdev, &gpio_devices, list) {
if (gdev->chip && match(gdev->chip, data))
@ -4730,7 +4730,7 @@ static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
s->private = "";
guard(mutex)(&gpio_devices_lock);
guard(rwsem_read)(&gpio_devices_sem);
list_for_each_entry(gdev, &gpio_devices, list) {
if (index-- == 0)
@ -4745,7 +4745,7 @@ static void *gpiolib_seq_next(struct seq_file *s, void *v, loff_t *pos)
struct gpio_device *gdev = v;
void *ret = NULL;
scoped_guard(mutex, &gpio_devices_lock) {
scoped_guard(rwsem_read, &gpio_devices_sem) {
if (list_is_last(&gdev->list, &gpio_devices))
ret = NULL;
else

2
drivers/gpio/gpiolib.h
View file

@ -137,7 +137,7 @@ int gpiod_set_transitory(struct gpio_desc *desc, bool transitory);
extern spinlock_t gpio_lock;
extern struct list_head gpio_devices;
extern struct mutex gpio_devices_lock;
extern struct rw_semaphore gpio_devices_sem;
void gpiod_line_state_notify(struct gpio_desc *desc, unsigned long action);