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: Richard Purdie <rpurdie@rpsys.net>

3 files changed, 30 insertions, 28 deletions

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 4211293ce862..ba8b04b03b9f 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -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);
diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
index 575368c2b100..0bdb786210b1 100644
--- a/drivers/leds/led-triggers.c
+++ b/drivers/leds/led-triggers.c
@@ -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);
 }
diff --git a/include/linux/leds.h b/include/linux/leds.h
index dc1178f6184b..b4130ff58d0c 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -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;