RTC: assure proper memory ordering with respect to RTC_DEV_BUSY flag
We must make sure that the RTC_DEV_BUSY flag has proper lock semantics,
i.e. that the RTC_DEV_BUSY stores clearing the flag don't get reordered
before the preceeding stores and loads and vice versa.
Spotted by Nick Piggin.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
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 a4f56e9..f1e00ff 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -293,7 +293,7 @@
return -EINVAL;
/* Cannot register while the char dev is in use */
- if (test_and_set_bit(RTC_DEV_BUSY, &rtc->flags))
+ if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))
return -EBUSY;
spin_lock_irq(&rtc->irq_task_lock);
@@ -303,7 +303,7 @@
}
spin_unlock_irq(&rtc->irq_task_lock);
- clear_bit(RTC_DEV_BUSY, &rtc->flags);
+ clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);
return retval;
}