1 files changed, 12 insertions, 3 deletions

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index ad66c6ecf365..a43afa54f0d7 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -210,6 +210,10 @@ int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
         if (task == NULL || task->func == NULL)
                 return -EINVAL;
 
+        /* Cannot register while the char dev is in use */
+        if (!(mutex_trylock(&rtc->char_lock)))
+                return -EBUSY;
+
         spin_lock_irq(&rtc->irq_task_lock);
         if (rtc->irq_task == NULL) {
                 rtc->irq_task = task;
@@ -217,13 +221,14 @@ int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
         }
         spin_unlock_irq(&rtc->irq_task_lock);
 
+        mutex_unlock(&rtc->char_lock);
+
         return retval;
 }
 EXPORT_SYMBOL_GPL(rtc_irq_register);
 
 void rtc_irq_unregister(struct rtc_device *rtc, struct rtc_task *task)
 {
-
         spin_lock_irq(&rtc->irq_task_lock);
         if (rtc->irq_task == task)
                 rtc->irq_task = NULL;
@@ -240,8 +245,10 @@ int rtc_irq_set_state(struct rtc_device *rtc, struct rtc_task *task, int enabled
                 return -ENXIO;
 
         spin_lock_irqsave(&rtc->irq_task_lock, flags);
+        if (rtc->irq_task != NULL && task == NULL)
+                err = -EBUSY;
         if (rtc->irq_task != task)
-                err = -ENXIO;
+                err = -EACCES;
         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 
         if (err == 0)
@@ -260,8 +267,10 @@ int rtc_irq_set_freq(struct rtc_device *rtc, struct rtc_task *task, int freq)
                 return -ENXIO;
 
         spin_lock_irqsave(&rtc->irq_task_lock, flags);
+        if (rtc->irq_task != NULL && task == NULL)
+                err = -EBUSY;
         if (rtc->irq_task != task)
-                err = -ENXIO;
+                err = -EACCES;
         spin_unlock_irqrestore(&rtc->irq_task_lock, flags);
 
         if (err == 0) {