rtc: interface: ignore expired timers when enqueuing new timers

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.

BugLink: http://bugs.launchpad.net/bugs/1333569
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 5836751b8203eb576a7af9f049c706ba27ee8d93..9bb934ed2a7a04adbb571e88c634f4ad97bb84f9 100644 (file)
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -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);