1 files changed, 28 insertions, 7 deletions

diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index 01bed937d387..f15a58f7403f 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -3000,12 +3000,16 @@ static struct backlight_ops ibm_backlight_data = {
         .update_status  = brightness_update_status,
 };
 
+static struct mutex brightness_mutex;
+
 static int __init brightness_init(struct ibm_init_struct *iibm)
 {
         int b;
 
         vdbg_printk(TPACPI_DBG_INIT, "initializing brightness subdriver\n");
 
+        mutex_init(&brightness_mutex);
+
         if (!brightness_mode) {
                 if (thinkpad_id.vendor == PCI_VENDOR_ID_LENOVO)
                         brightness_mode = 2;
@@ -3092,27 +3096,44 @@ static int brightness_get(struct backlight_device *bd)
 
 static int brightness_set(int value)
 {
-        int cmos_cmd, inc, i;
-        int current_value = brightness_get(NULL);
+        int cmos_cmd, inc, i, res;
+        int current_value;
 
         if (value > 7)
                 return -EINVAL;
 
+        res = mutex_lock_interruptible(&brightness_mutex);
+        if (res < 0)
+                return res;
+
+        current_value = brightness_get(NULL);
+        if (current_value < 0) {
+                res = current_value;
+                goto errout;
+        }
+
         cmos_cmd = value > current_value ?
                         TP_CMOS_BRIGHTNESS_UP :
                         TP_CMOS_BRIGHTNESS_DOWN;
         inc = value > current_value ? 1 : -1;
 
+        res = 0;
         for (i = current_value; i != value; i += inc) {
                 if ((brightness_mode & 2) &&
-                    issue_thinkpad_cmos_command(cmos_cmd))
-                        return -EIO;
+                    issue_thinkpad_cmos_command(cmos_cmd)) {
+                        res = -EIO;
+                        goto errout;
+                }
                 if ((brightness_mode & 1) &&
-                    !acpi_ec_write(brightness_offset, i + inc))
-                        return -EIO;
+                    !acpi_ec_write(brightness_offset, i + inc)) {
+                        res = -EIO;
+                        goto errout;;
+                }
         }
 
-        return 0;
+errout:
+        mutex_unlock(&brightness_mutex);
+        return res;
 }
 
 static int brightness_read(char *p)