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    Subject[PATCH 3.16 006/136] rtc: interface: ignore expired timers when enqueuing new timers
    3.16.54-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Colin Ian King <colin.king@canonical.com>

    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>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/rtc/interface.c | 16 +++++++++++++++-
    1 file changed, 15 insertions(+), 1 deletion(-)

    --- a/drivers/rtc/interface.c
    +++ b/drivers/rtc/interface.c
    @@ -778,9 +778,23 @@ 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);
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