Commit dc47206e authored by Richard Purdie's avatar Richard Purdie
Browse files

leds: Fix led trigger locking bugs 



Convert part of the led trigger core from rw spinlocks to rw
semaphores. We're calling functions which can sleep from invalid
contexts otherwise. Fixes bug #9264.

Signed-off-by: default avatarRichard Purdie <rpurdie@rpsys.net>
parent f194d132

drivers/leds/led-class.c

+3 −3
Original line number Diff line number Diff line
@@ -111,7 +111,7 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev) 
	write_unlock(&leds_list_lock);



#ifdef CONFIG_LEDS_TRIGGERS

	rwlock_init(&led_cdev->trigger_lock);

	init_rwsem(&led_cdev->trigger_lock);



	rc = device_create_file(led_cdev->dev, &dev_attr_trigger);

	if (rc)
@@ -147,10 +147,10 @@ void led_classdev_unregister(struct led_classdev *led_cdev) 
	device_remove_file(led_cdev->dev, &dev_attr_brightness);

#ifdef CONFIG_LEDS_TRIGGERS

	device_remove_file(led_cdev->dev, &dev_attr_trigger);

	write_lock(&led_cdev->trigger_lock);

	down_write(&led_cdev->trigger_lock);

	if (led_cdev->trigger)

		led_trigger_set(led_cdev, NULL);

	write_unlock(&led_cdev->trigger_lock);

	up_write(&led_cdev->trigger_lock);

#endif



	device_unregister(led_cdev->dev);

drivers/leds/led-triggers.c

+25 −24
Original line number Diff line number Diff line
@@ -19,13 +19,14 @@ 
#include <linux/device.h>

#include <linux/sysdev.h>

#include <linux/timer.h>

#include <linux/rwsem.h>

#include <linux/leds.h>

#include "leds.h"



/*

 * Nests outside led_cdev->trigger_lock

 */

static DEFINE_RWLOCK(triggers_list_lock);

static DECLARE_RWSEM(triggers_list_lock);

static LIST_HEAD(trigger_list);



ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr,
@@ -44,24 +45,24 @@ ssize_t led_trigger_store(struct device *dev, struct device_attribute *attr, 
		trigger_name[len - 1] = '\0';



	if (!strcmp(trigger_name, "none")) {

		write_lock(&led_cdev->trigger_lock);

		down_write(&led_cdev->trigger_lock);

		led_trigger_set(led_cdev, NULL);

		write_unlock(&led_cdev->trigger_lock);

		up_write(&led_cdev->trigger_lock);

		return count;

	}



	read_lock(&triggers_list_lock);

	down_read(&triggers_list_lock);

	list_for_each_entry(trig, &trigger_list, next_trig) {

		if (!strcmp(trigger_name, trig->name)) {

			write_lock(&led_cdev->trigger_lock);

			down_write(&led_cdev->trigger_lock);

			led_trigger_set(led_cdev, trig);

			write_unlock(&led_cdev->trigger_lock);

			up_write(&led_cdev->trigger_lock);



			read_unlock(&triggers_list_lock);

			up_read(&triggers_list_lock);

			return count;

		}

	}

	read_unlock(&triggers_list_lock);

	up_read(&triggers_list_lock);



	return -EINVAL;

}
@@ -74,8 +75,8 @@ ssize_t led_trigger_show(struct device *dev, struct device_attribute *attr, 
	struct led_trigger *trig;

	int len = 0;



	read_lock(&triggers_list_lock);

	read_lock(&led_cdev->trigger_lock);

	down_read(&triggers_list_lock);

	down_read(&led_cdev->trigger_lock);



	if (!led_cdev->trigger)

		len += sprintf(buf+len, "[none] ");
@@ -89,8 +90,8 @@ ssize_t led_trigger_show(struct device *dev, struct device_attribute *attr, 
		else

			len += sprintf(buf+len, "%s ", trig->name);

	}

	read_unlock(&led_cdev->trigger_lock);

	read_unlock(&triggers_list_lock);

	up_read(&led_cdev->trigger_lock);

	up_read(&triggers_list_lock);



	len += sprintf(len+buf, "\n");

	return len;
@@ -145,14 +146,14 @@ void led_trigger_set_default(struct led_classdev *led_cdev) 
	if (!led_cdev->default_trigger)

		return;



	read_lock(&triggers_list_lock);

	write_lock(&led_cdev->trigger_lock);

	down_read(&triggers_list_lock);

	down_write(&led_cdev->trigger_lock);

	list_for_each_entry(trig, &trigger_list, next_trig) {

		if (!strcmp(led_cdev->default_trigger, trig->name))

			led_trigger_set(led_cdev, trig);

	}

	write_unlock(&led_cdev->trigger_lock);

	read_unlock(&triggers_list_lock);

	up_write(&led_cdev->trigger_lock);

	up_read(&triggers_list_lock);

}



int led_trigger_register(struct led_trigger *trigger)
@@ -163,18 +164,18 @@ int led_trigger_register(struct led_trigger *trigger) 
	INIT_LIST_HEAD(&trigger->led_cdevs);



	/* Add to the list of led triggers */

	write_lock(&triggers_list_lock);

	down_write(&triggers_list_lock);

	list_add_tail(&trigger->next_trig, &trigger_list);

	write_unlock(&triggers_list_lock);

	up_write(&triggers_list_lock);



	/* Register with any LEDs that have this as a default trigger */

	read_lock(&leds_list_lock);

	list_for_each_entry(led_cdev, &leds_list, node) {

		write_lock(&led_cdev->trigger_lock);

		down_write(&led_cdev->trigger_lock);

		if (!led_cdev->trigger && led_cdev->default_trigger &&

			    !strcmp(led_cdev->default_trigger, trigger->name))

			led_trigger_set(led_cdev, trigger);

		write_unlock(&led_cdev->trigger_lock);

		up_write(&led_cdev->trigger_lock);

	}

	read_unlock(&leds_list_lock);
@@ -206,17 +207,17 @@ void led_trigger_unregister(struct led_trigger *trigger) 
	struct led_classdev *led_cdev;



	/* Remove from the list of led triggers */

	write_lock(&triggers_list_lock);

	down_write(&triggers_list_lock);

	list_del(&trigger->next_trig);

	write_unlock(&triggers_list_lock);

	up_write(&triggers_list_lock);



	/* Remove anyone actively using this trigger */

	read_lock(&leds_list_lock);

	list_for_each_entry(led_cdev, &leds_list, node) {

		write_lock(&led_cdev->trigger_lock);

		down_write(&led_cdev->trigger_lock);

		if (led_cdev->trigger == trigger)

			led_trigger_set(led_cdev, NULL);

		write_unlock(&led_cdev->trigger_lock);

		up_write(&led_cdev->trigger_lock);

	}

	read_unlock(&leds_list_lock);

}

include/linux/leds.h

+2 −1
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 


#include <linux/list.h>

#include <linux/spinlock.h>

#include <linux/rwsem.h>



struct device;

/*
@@ -43,7 +44,7 @@ struct led_classdev { 


#ifdef CONFIG_LEDS_TRIGGERS

	/* Protects the trigger data below */

	rwlock_t		 trigger_lock;

	struct rw_semaphore	 trigger_lock;



	struct led_trigger	*trigger;

	struct list_head	 trig_list;