RTC: convert mutex to bitfield

RTC code is using mutex to assure exclusive access to /dev/rtc.  This is
however wrong usage, as it leaves the mutex locked when returning into
userspace, which is unacceptable.

Convert rtc->char_lock into bit operation.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index de0da54..a4f56e9 100644 (file)
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -293,7 +293,7 @@ int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
                return -EINVAL;
 
        /* Cannot register while the char dev is in use */
-       if (!(mutex_trylock(&rtc->char_lock)))
+       if (test_and_set_bit(RTC_DEV_BUSY, &rtc->flags))
                return -EBUSY;
 
        spin_lock_irq(&rtc->irq_task_lock);
@@ -303,7 +303,7 @@ int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task)
        }
        spin_unlock_irq(&rtc->irq_task_lock);
 
-       mutex_unlock(&rtc->char_lock);
+       clear_bit(RTC_DEV_BUSY, &rtc->flags);
 
        return retval;
 }

diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index 814583b..ae1bf17 100644 (file)
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -26,10 +26,7 @@ static int rtc_dev_open(struct inode *inode, struct file *file)
                                        struct rtc_device, char_dev);
        const struct rtc_class_ops *ops = rtc->ops;
 
-       /* We keep the lock as long as the device is in use
-        * and return immediately if busy
-        */
-       if (!(mutex_trylock(&rtc->char_lock)))
+       if (test_and_set_bit(RTC_DEV_BUSY, &rtc->flags))
                return -EBUSY;
 
        file->private_data = rtc;
@@ -43,8 +40,8 @@ static int rtc_dev_open(struct inode *inode, struct file *file)
                return 0;
        }
 
-       /* something has gone wrong, release the lock */
-       mutex_unlock(&rtc->char_lock);
+       /* something has gone wrong */
+       clear_bit(RTC_DEV_BUSY, &rtc->flags);
        return err;
 }
 
@@ -405,7 +402,7 @@ static int rtc_dev_release(struct inode *inode, struct file *file)
        if (rtc->ops->release)
                rtc->ops->release(rtc->dev.parent);
 
-       mutex_unlock(&rtc->char_lock);
+       clear_bit(RTC_DEV_BUSY, &rtc->flags);
        return 0;
 }
 
@@ -440,7 +437,6 @@ void rtc_dev_prepare(struct rtc_device *rtc)
 
        rtc->dev.devt = MKDEV(MAJOR(rtc_devt), rtc->id);
 
-       mutex_init(&rtc->char_lock);
 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
        INIT_WORK(&rtc->uie_task, rtc_uie_task);
        setup_timer(&rtc->uie_timer, rtc_uie_timer, (unsigned long)rtc);

diff --git a/include/linux/rtc.h b/include/linux/rtc.h
index 6d5e4a4..f2d0d15 100644 (file)
--- a/include/linux/rtc.h
+++ b/include/linux/rtc.h
@@ -133,6 +133,9 @@ struct rtc_class_ops {
 #define RTC_DEVICE_NAME_SIZE 20
 struct rtc_task;
 
+/* flags */
+#define RTC_DEV_BUSY 0
+
 struct rtc_device
 {
        struct device dev;
@@ -145,7 +148,7 @@ struct rtc_device
        struct mutex ops_lock;
 
        struct cdev char_dev;
-       struct mutex char_lock;
+       unsigned long flags;
 
        unsigned long irq_data;
        spinlock_t irq_lock;