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Johannes pointed out that locking is still problematic with triggers 

list, attempt to solve that by using RCU.
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Merge tag 'leds-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/pavel/linux-leds

Pull LED updates from Pavel Machek:
 "Johannes pointed out that locking is still problematic with triggers
  list, attempt to solve that by using RCU"

* tag 'leds-5.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/pavel/linux-leds:
  leds: trigger: Disable CPU trigger on PREEMPT_RT
  leds: trigger: use RCU to protect the led_cdevs list
  led-class-flash: fix -Wrestrict warning
This commit is contained in:
Linus Torvalds 2021-11-01 18:49:25 -07:00
parent 73d21a3579 97b31c1f8e
commit 4dee060625
4 changed files with 24 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/leds/led-class-flash.c
View File

@ -207,7 +207,7 @@ static ssize_t flash_fault_show(struct device *dev,
mask <<= 1;
}
return sprintf(buf, "%s\n", buf);
return strlen(strcat(buf, "\n"));
}
static DEVICE_ATTR_RO(flash_fault);

41
drivers/leds/led-triggers.c
View File

@ -157,7 +157,6 @@ EXPORT_SYMBOL_GPL(led_trigger_read);
/* Caller must ensure led_cdev->trigger_lock held */
int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
{
unsigned long flags;
char *event = NULL;
char *envp[2];
const char *name;
@ -171,10 +170,13 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
/* Remove any existing trigger */
if (led_cdev->trigger) {
write_lock_irqsave(&led_cdev->trigger->leddev_list_lock, flags);
list_del(&led_cdev->trig_list);
write_unlock_irqrestore(&led_cdev->trigger->leddev_list_lock,
flags);
spin_lock(&led_cdev->trigger->leddev_list_lock);
list_del_rcu(&led_cdev->trig_list);
spin_unlock(&led_cdev->trigger->leddev_list_lock);
/* ensure it's no longer visible on the led_cdevs list */
synchronize_rcu();
cancel_work_sync(&led_cdev->set_brightness_work);
led_stop_software_blink(led_cdev);
if (led_cdev->trigger->deactivate)
@ -186,9 +188,9 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
led_set_brightness(led_cdev, LED_OFF);
}
if (trig) {
write_lock_irqsave(&trig->leddev_list_lock, flags);
list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
write_unlock_irqrestore(&trig->leddev_list_lock, flags);
spin_lock(&trig->leddev_list_lock);
list_add_tail_rcu(&led_cdev->trig_list, &trig->led_cdevs);
spin_unlock(&trig->leddev_list_lock);
led_cdev->trigger = trig;
if (trig->activate)
@ -223,9 +225,10 @@ err_add_groups:
trig->deactivate(led_cdev);
err_activate:
write_lock_irqsave(&led_cdev->trigger->leddev_list_lock, flags);
list_del(&led_cdev->trig_list);
write_unlock_irqrestore(&led_cdev->trigger->leddev_list_lock, flags);
spin_lock(&led_cdev->trigger->leddev_list_lock);
list_del_rcu(&led_cdev->trig_list);
spin_unlock(&led_cdev->trigger->leddev_list_lock);
synchronize_rcu();
led_cdev->trigger = NULL;
led_cdev->trigger_data = NULL;
led_set_brightness(led_cdev, LED_OFF);
@ -285,7 +288,7 @@ int led_trigger_register(struct led_trigger *trig)
struct led_classdev *led_cdev;
struct led_trigger *_trig;
rwlock_init(&trig->leddev_list_lock);
spin_lock_init(&trig->leddev_list_lock);
INIT_LIST_HEAD(&trig->led_cdevs);
down_write(&triggers_list_lock);
@ -378,15 +381,14 @@ void led_trigger_event(struct led_trigger *trig,
enum led_brightness brightness)
{
struct led_classdev *led_cdev;
unsigned long flags;
if (!trig)
return;
read_lock_irqsave(&trig->leddev_list_lock, flags);
list_for_each_entry(led_cdev, &trig->led_cdevs, trig_list)
rcu_read_lock();
list_for_each_entry_rcu(led_cdev, &trig->led_cdevs, trig_list)
led_set_brightness(led_cdev, brightness);
read_unlock_irqrestore(&trig->leddev_list_lock, flags);
rcu_read_unlock();
}
EXPORT_SYMBOL_GPL(led_trigger_event);
@ -397,20 +399,19 @@ static void led_trigger_blink_setup(struct led_trigger *trig,
int invert)
{
struct led_classdev *led_cdev;
unsigned long flags;
if (!trig)
return;
read_lock_irqsave(&trig->leddev_list_lock, flags);
list_for_each_entry(led_cdev, &trig->led_cdevs, trig_list) {
rcu_read_lock();
list_for_each_entry_rcu(led_cdev, &trig->led_cdevs, trig_list) {
if (oneshot)
led_blink_set_oneshot(led_cdev, delay_on, delay_off,
invert);
else
led_blink_set(led_cdev, delay_on, delay_off);
}
read_unlock_irqrestore(&trig->leddev_list_lock, flags);
rcu_read_unlock();
}
void led_trigger_blink(struct led_trigger *trig,

1
drivers/leds/trigger/Kconfig
View File

@ -64,6 +64,7 @@ config LEDS_TRIGGER_BACKLIGHT
config LEDS_TRIGGER_CPU
bool "LED CPU Trigger"
depends on !PREEMPT_RT
help
This allows LEDs to be controlled by active CPUs. This shows
the active CPUs across an array of LEDs so you can see which

2
include/linux/leds.h
View File

@ -360,7 +360,7 @@ struct led_trigger {
struct led_hw_trigger_type *trigger_type;
/* LEDs under control by this trigger (for simple triggers) */
rwlock_t leddev_list_lock;
spinlock_t leddev_list_lock;
struct list_head led_cdevs;
/* Link to next registered trigger */