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[PATCH] rtc: interface: ignore exprired timers one enqueing new timers

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  [PATCH] rtc: interface: ignore exprired timers one enqueing new timers Colin King <colin.king@canonical.com> - 2016-05-16 18:30 +0200
    Re: [PATCH] rtc: interface: ignore exprired timers one enqueing new  timers Alexandre Belloni <alexandre.belloni@free-electrons.com> - 2016-05-19 18:40 +0200

#1401610 — [PATCH] rtc: interface: ignore exprired timers one enqueing new timers

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

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

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 9ef5f6f..7fa910f 100644
--- 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);
-- 
2.7.4

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#1403849 — Re: [PATCH] rtc: interface: ignore exprired timers one enqueing new timers

Hi Colin,

On 16/05/2016 at 17:22:54 +0100, Colin King wrote :
> From: Colin Ian King <colin.king@canonical.com>
> 
> 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 repead 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>

Thanks for the resend. I was still planning to have a look at the patch
you send in September 2014. I believe that one replaces it.

I'll definitely have a look after 4.7-rc1.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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