Patch "rtc: interface: ignore expired timers when enqueuing new timers" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

rtc: interface: ignore expired timers when enqueuing new timers

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
rtc-interface-ignore-expired-timers-when-enqueuing-new-timers.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Colin Ian King <[email protected]>
Date: Mon, 16 May 2016 17:22:54 +0100
Subject: rtc: interface: ignore expired timers when enqueuing new timers

From: Colin Ian King <[email protected]>

commit 2b2f5ff00f63847d95adad6289bd8b05f5983dd5 upstream.

This patch fixes a RTC wakealarm issue, namely, the event fires during hibernate and is not cleared from the list, causing hwclock to block.

The current enqueuing does not trigger an alarm if any expired timers already exist on the timerqueue. This can occur when a RTC wake alarm is used to wake a machine out of hibernate and the resumed state has old expired timers that have not been removed from the timer queue. This fix skips over any expired timers and triggers an alarm if there are no pending timers on the timerqueue. Note that the skipped expired timer will get reaped later on, so there is no need to clean it up immediately.

The issue can be reproduced by putting a machine into hibernate and waking it with the RTC wakealarm. Running the example RTC test program from tools/testing/selftests/timers/rtctest.c after the hibernate will block indefinitely. With the fix, it no longer blocks after the hibernate resume.

---
 drivers/rtc/interface.c |   16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

@@ -748,9 +748,23 @@ EXPORT_SYMBOL_GPL(rtc_irq_set_freq);
  */
 static int rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer)
 {
+	struct timerqueue_node *next = timerqueue_getnext(&rtc->timerqueue);
+	struct rtc_time tm;
+	ktime_t now;
+
 	timer->enabled = 1;
+	__rtc_read_time(rtc, &tm);
+	now = rtc_tm_to_ktime(tm);
+
+	/* Skip over expired timers */
+	while (next) {
+		if (next->expires.tv64 >= now.tv64)
+			break;
+		next = timerqueue_iterate_next(next);
+	}
+
 	timerqueue_add(&rtc->timerqueue, &timer->node);
-	if (&timer->node == timerqueue_getnext(&rtc->timerqueue)) {
+	if (!next) {
 		struct rtc_wkalrm alarm;
 		int err;
 		alarm.time = rtc_ktime_to_tm(timer->node.expires);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/rtc-interface-ignore-expired-timers-when-enqueuing-new-timers.patch