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>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index de0da545c7a1..a4f56e95cf96 100644
--- 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;
 }