@@ -2,6 +2,7 @@
#include <linux/acpi.h>
#include <linux/bitmap.h>
+#include <linux/cleanup.h>
#include <linux/compat.h>
#include <linux/debugfs.h>
#include <linux/device.h>
@@ -14,12 +15,14 @@
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/list.h>
+#include <linux/lockdep.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/pinctrl/consumer.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
+#include <linux/srcu.h>
#include <linux/string.h>
#include <linux/gpio.h>
@@ -81,7 +84,12 @@ DEFINE_SPINLOCK(gpio_lock);
static DEFINE_MUTEX(gpio_lookup_lock);
static LIST_HEAD(gpio_lookup_list);
+
LIST_HEAD(gpio_devices);
+/* Protects the GPIO device list against concurrent modifications. */
+static DEFINE_MUTEX(gpio_devices_lock);
+/* Ensures coherence during read-only accesses to the list of GPIO devices. */
+DEFINE_STATIC_SRCU(gpio_devices_srcu);
static DEFINE_MUTEX(gpio_machine_hogs_mutex);
static LIST_HEAD(gpio_machine_hogs);
@@ -113,20 +121,16 @@ static inline void desc_set_label(struct gpio_desc *d, const char *label)
struct gpio_desc *gpio_to_desc(unsigned gpio)
{
struct gpio_device *gdev;
- unsigned long flags;
- spin_lock_irqsave(&gpio_lock, flags);
-
- list_for_each_entry(gdev, &gpio_devices, list) {
- if (gdev->base <= gpio &&
- gdev->base + gdev->ngpio > gpio) {
- spin_unlock_irqrestore(&gpio_lock, flags);
- return &gdev->descs[gpio - gdev->base];
+ scoped_guard(srcu, &gpio_devices_srcu) {
+ list_for_each_entry_srcu(gdev, &gpio_devices, list,
+ srcu_read_lock_held(&gpio_devices_srcu)) {
+ if (gdev->base <= gpio &&
+ gdev->base + gdev->ngpio > gpio)
+ return &gdev->descs[gpio - gdev->base];
}
}
- spin_unlock_irqrestore(&gpio_lock, flags);
-
if (!gpio_is_valid(gpio))
pr_warn("invalid GPIO %d\n", gpio);
@@ -282,7 +286,8 @@ static int gpiochip_find_base_unlocked(int ngpio)
struct gpio_device *gdev;
int base = GPIO_DYNAMIC_BASE;
- list_for_each_entry(gdev, &gpio_devices, list) {
+ list_for_each_entry_srcu(gdev, &gpio_devices, list,
+ lockdep_is_held(&gpio_devices_lock)) {
/* found a free space? */
if (gdev->base >= base + ngpio)
break;
@@ -354,23 +359,25 @@ static int gpiodev_add_to_list_unlocked(struct gpio_device *gdev)
{
struct gpio_device *prev, *next;
+ lockdep_assert_held(&gpio_devices_lock);
+
if (list_empty(&gpio_devices)) {
/* initial entry in list */
- list_add_tail(&gdev->list, &gpio_devices);
+ list_add_tail_rcu(&gdev->list, &gpio_devices);
return 0;
}
next = list_first_entry(&gpio_devices, struct gpio_device, list);
if (gdev->base + gdev->ngpio <= next->base) {
/* add before first entry */
- list_add(&gdev->list, &gpio_devices);
+ list_add_rcu(&gdev->list, &gpio_devices);
return 0;
}
prev = list_last_entry(&gpio_devices, struct gpio_device, list);
if (prev->base + prev->ngpio <= gdev->base) {
/* add behind last entry */
- list_add_tail(&gdev->list, &gpio_devices);
+ list_add_tail_rcu(&gdev->list, &gpio_devices);
return 0;
}
@@ -382,11 +389,13 @@ static int gpiodev_add_to_list_unlocked(struct gpio_device *gdev)
/* add between prev and next */
if (prev->base + prev->ngpio <= gdev->base
&& gdev->base + gdev->ngpio <= next->base) {
- list_add(&gdev->list, &prev->list);
+ list_add_rcu(&gdev->list, &prev->list);
return 0;
}
}
+ synchronize_srcu(&gpio_devices_srcu);
+
return -EBUSY;
}
@@ -399,26 +408,21 @@ static int gpiodev_add_to_list_unlocked(struct gpio_device *gdev)
static struct gpio_desc *gpio_name_to_desc(const char * const name)
{
struct gpio_device *gdev;
- unsigned long flags;
+ struct gpio_desc *desc;
if (!name)
return NULL;
- spin_lock_irqsave(&gpio_lock, flags);
-
- list_for_each_entry(gdev, &gpio_devices, list) {
- struct gpio_desc *desc;
+ guard(srcu)(&gpio_devices_srcu);
+ list_for_each_entry_srcu(gdev, &gpio_devices, list,
+ srcu_read_lock_held(&gpio_devices_srcu)) {
for_each_gpio_desc(gdev->chip, desc) {
- if (desc->name && !strcmp(desc->name, name)) {
- spin_unlock_irqrestore(&gpio_lock, flags);
+ if (desc->name && !strcmp(desc->name, name))
return desc;
- }
}
}
- spin_unlock_irqrestore(&gpio_lock, flags);
-
return NULL;
}
@@ -748,7 +752,10 @@ static void gpiochip_setup_devs(void)
struct gpio_device *gdev;
int ret;
- list_for_each_entry(gdev, &gpio_devices, list) {
+ guard(srcu)(&gpio_devices_srcu);
+
+ list_for_each_entry_srcu(gdev, &gpio_devices, list,
+ srcu_read_lock_held(&gpio_devices_srcu)) {
ret = gpiochip_setup_dev(gdev);
if (ret)
dev_err(&gdev->dev,
@@ -813,7 +820,6 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
struct lock_class_key *request_key)
{
struct gpio_device *gdev;
- unsigned long flags;
unsigned int i;
int base = 0;
int ret = 0;
@@ -878,49 +884,47 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
gdev->ngpio = gc->ngpio;
- spin_lock_irqsave(&gpio_lock, flags);
-
- /*
- * TODO: this allocates a Linux GPIO number base in the global
- * GPIO numberspace for this chip. In the long run we want to
- * get *rid* of this numberspace and use only descriptors, but
- * it may be a pipe dream. It will not happen before we get rid
- * of the sysfs interface anyways.
- */
- base = gc->base;
- if (base < 0) {
- base = gpiochip_find_base_unlocked(gc->ngpio);
+ scoped_guard(mutex, &gpio_devices_lock) {
+ /*
+ * TODO: this allocates a Linux GPIO number base in the global
+ * GPIO numberspace for this chip. In the long run we want to
+ * get *rid* of this numberspace and use only descriptors, but
+ * it may be a pipe dream. It will not happen before we get rid
+ * of the sysfs interface anyways.
+ */
+ base = gc->base;
if (base < 0) {
- spin_unlock_irqrestore(&gpio_lock, flags);
- ret = base;
- base = 0;
+ base = gpiochip_find_base_unlocked(gc->ngpio);
+ if (base < 0) {
+ ret = base;
+ base = 0;
+ goto err_free_label;
+ }
+
+ /*
+ * TODO: it should not be necessary to reflect the
+ * assigned base outside of the GPIO subsystem. Go over
+ * drivers and see if anyone makes use of this, else
+ * drop this and assign a poison instead.
+ */
+ gc->base = base;
+ } else {
+ dev_warn(&gdev->dev,
+ "Static allocation of GPIO base is deprecated, use dynamic allocation.\n");
+ }
+
+ gdev->base = base;
+
+ ret = gpiodev_add_to_list_unlocked(gdev);
+ if (ret) {
+ chip_err(gc, "GPIO integer space overlap, cannot add chip\n");
goto err_free_label;
}
- /*
- * TODO: it should not be necessary to reflect the assigned
- * base outside of the GPIO subsystem. Go over drivers and
- * see if anyone makes use of this, else drop this and assign
- * a poison instead.
- */
- gc->base = base;
- } else {
- dev_warn(&gdev->dev,
- "Static allocation of GPIO base is deprecated, use dynamic allocation.\n");
- }
- gdev->base = base;
-
- ret = gpiodev_add_to_list_unlocked(gdev);
- if (ret) {
- spin_unlock_irqrestore(&gpio_lock, flags);
- chip_err(gc, "GPIO integer space overlap, cannot add chip\n");
- goto err_free_label;
}
for (i = 0; i < gc->ngpio; i++)
gdev->descs[i].gdev = gdev;
- spin_unlock_irqrestore(&gpio_lock, flags);
-
BLOCKING_INIT_NOTIFIER_HEAD(&gdev->line_state_notifier);
BLOCKING_INIT_NOTIFIER_HEAD(&gdev->device_notifier);
init_rwsem(&gdev->sem);
@@ -1011,9 +1015,9 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
goto err_print_message;
}
err_remove_from_list:
- spin_lock_irqsave(&gpio_lock, flags);
- list_del(&gdev->list);
- spin_unlock_irqrestore(&gpio_lock, flags);
+ scoped_guard(mutex, &gpio_devices_lock)
+ list_del_rcu(&gdev->list);
+ synchronize_srcu(&gpio_devices_srcu);
err_free_label:
kfree_const(gdev->label);
err_free_descs:
@@ -1076,8 +1080,9 @@ void gpiochip_remove(struct gpio_chip *gc)
dev_crit(&gdev->dev,
"REMOVING GPIOCHIP WITH GPIOS STILL REQUESTED\n");
- scoped_guard(spinlock_irqsave, &gpio_lock)
- list_del(&gdev->list);
+ scoped_guard(mutex, &gpio_devices_lock)
+ list_del_rcu(&gdev->list);
+ synchronize_srcu(&gpio_devices_srcu);
/*
* The gpiochip side puts its use of the device to rest here:
@@ -1125,7 +1130,7 @@ struct gpio_device *gpio_device_find(void *data,
*/
might_sleep();
- guard(spinlock_irqsave)(&gpio_lock);
+ guard(srcu)(&gpio_devices_srcu);
list_for_each_entry(gdev, &gpio_devices, list) {
if (gdev->chip && match(gdev->chip, data))
@@ -4133,30 +4138,39 @@ static struct gpio_desc *gpiod_find_and_request(struct device *consumer,
bool platform_lookup_allowed)
{
unsigned long lookupflags = GPIO_LOOKUP_FLAGS_DEFAULT;
- struct gpio_desc *desc;
- int ret;
-
- desc = gpiod_find_by_fwnode(fwnode, consumer, con_id, idx, &flags, &lookupflags);
- if (gpiod_not_found(desc) && platform_lookup_allowed) {
- /*
- * Either we are not using DT or ACPI, or their lookup did not
- * return a result. In that case, use platform lookup as a
- * fallback.
- */
- dev_dbg(consumer, "using lookup tables for GPIO lookup\n");
- desc = gpiod_find(consumer, con_id, idx, &lookupflags);
- }
-
- if (IS_ERR(desc)) {
- dev_dbg(consumer, "No GPIO consumer %s found\n", con_id);
- return desc;
- }
-
/*
- * If a connection label was passed use that, else attempt to use
- * the device name as label
+ * scoped_guard() is implemented as a for loop, meaning static
+ * analyzers will complain about these two not being initialized.
*/
- ret = gpiod_request(desc, label);
+ struct gpio_desc *desc = NULL;
+ int ret = 0;
+
+ scoped_guard(srcu, &gpio_devices_srcu) {
+ desc = gpiod_find_by_fwnode(fwnode, consumer, con_id, idx,
+ &flags, &lookupflags);
+ if (gpiod_not_found(desc) && platform_lookup_allowed) {
+ /*
+ * Either we are not using DT or ACPI, or their lookup
+ * did not return a result. In that case, use platform
+ * lookup as a fallback.
+ */
+ dev_dbg(consumer,
+ "using lookup tables for GPIO lookup\n");
+ desc = gpiod_find(consumer, con_id, idx, &lookupflags);
+ }
+
+ if (IS_ERR(desc)) {
+ dev_dbg(consumer, "No GPIO consumer %s found\n",
+ con_id);
+ return desc;
+ }
+
+ /*
+ * If a connection label was passed use that, else attempt to use
+ * the device name as label
+ */
+ ret = gpiod_request(desc, label);
+ }
if (ret) {
if (!(ret == -EBUSY && flags & GPIOD_FLAGS_BIT_NONEXCLUSIVE))
return ERR_PTR(ret);
@@ -4727,35 +4741,33 @@ static void gpiolib_dbg_show(struct seq_file *s, struct gpio_device *gdev)
static void *gpiolib_seq_start(struct seq_file *s, loff_t *pos)
{
- unsigned long flags;
struct gpio_device *gdev = NULL;
loff_t index = *pos;
s->private = "";
- spin_lock_irqsave(&gpio_lock, flags);
- list_for_each_entry(gdev, &gpio_devices, list)
- if (index-- == 0) {
- spin_unlock_irqrestore(&gpio_lock, flags);
+ guard(srcu)(&gpio_devices_srcu);
+
+ list_for_each_entry(gdev, &gpio_devices, list) {
+ if (index-- == 0)
return gdev;
- }
- spin_unlock_irqrestore(&gpio_lock, flags);
+ }
return NULL;
}
static void *gpiolib_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
- unsigned long flags;
struct gpio_device *gdev = v;
void *ret = NULL;
- spin_lock_irqsave(&gpio_lock, flags);
- if (list_is_last(&gdev->list, &gpio_devices))
- ret = NULL;
- else
- ret = list_first_entry(&gdev->list, struct gpio_device, list);
- spin_unlock_irqrestore(&gpio_lock, flags);
+ scoped_guard(srcu, &gpio_devices_srcu) {
+ if (list_is_last(&gdev->list, &gpio_devices))
+ ret = NULL;
+ else
+ ret = list_first_entry(&gdev->list, struct gpio_device,
+ list);
+ }
s->private = "\n";
++*pos;