rtc: file close() consistently disables repeating irqs

Make the rtc framework consistent about disabling 1/second update IRQs
that may have been activated through the /dev interface, when that /dev
file is closed.  (It may have closed because of coredump, etc.) This was
previously done only for emulated update IRQs ...  now, do it always.

Also comment the current policy: repeating IRQs (periodic, update) that
userspace enabled will be cleanly disabled, but alarms are left alone.
Such repeating IRQs are a constant and pointless system load.

Update some RTC drivers to remove now-needless release() methods.  Most
such methods just enforce that policy.  The others all seem to be buggy,
and mistreat in-kernel clients of periodic or alarm IRQs.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Acked-by: Andrew Sharp <andy.sharp@onstor.com>
Cc: Angelo Castello <angelo.castello@st.com>
Acked-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Cc: Thomas Hommel <thomas.hommel@gefanuc.com>
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>

1 files changed, 9 insertions, 3 deletions

diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index 52e2743b04ec..079e9ed907e0 100644
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -432,9 +432,15 @@ static int rtc_dev_release(struct inode *inode, struct file *file)
 {
         struct rtc_device *rtc = file->private_data;
 
-#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
-        clear_uie(rtc);
-#endif
+        /* We shut down the repeating IRQs that userspace enabled,
+         * since nothing is listening to them.
+         *  - Update (UIE) ... currently only managed through ioctls
+         *  - Periodic (PIE) ... also used through rtc_*() interface calls
+         *
+         * Leave the alarm alone; it may be set to trigger a system wakeup
+         * later, or be used by kernel code, and is a one-shot event anyway.
+         */
+        rtc_dev_ioctl(file, RTC_UIE_OFF, 0);
         rtc_irq_set_state(rtc, NULL, 0);
 
         if (rtc->ops->release)