Hardware specific rtc regression in v4.4.76

Hardware specific rtc regression in v4.4.76

[elseifthen]

Hello all,

There appears to be a hardware specific rtc regression in v4.4.76.

Introduced in v4.4.52 by:

commit f0414c1f8bb7a4e69064296f460773170c5435ac
Author: Colin Ian King <colin.king@canonical.com>
Date:   Mon May 16 17:22:54 2016 +0100

    rtc: interface: ignore expired timers when enqueuing new timers
    
    commit 2b2f5ff00f63847d95adad6289bd8b05f5983dd5 upstream.

 8< ---

The problem does not appear to be in v4.9.x kernels.

Maybe v4.4.76 is missing one of these?
http://marc.info/?l=linux-rtc&m=149489307123605&w=2
Which also includes the commit in question.

See this thread for more details:
https://www.linuxquestions.org/questions/slackware-14/slow-hwclock-systohc-on-reboot-shutdown-4175609040/

Note: I am not the one having this issue. I'm only reporting it, so any
questions would need to be asked in the above thread. Or perhaps the
person with the problem will follow this email thread. I will post a
link to it for them.

Re: Hardware specific rtc regression in v4.4.76

[Alexandre Belloni]

Hi,

Thanks for the report.

On 06/07/2017 at 15:16:11 -0400, elseifthen@gmx.com wrote:
> There appears to be a hardware specific rtc regression in v4.4.76.
> 
> Introduced in v4.4.52 by:
> 
> commit f0414c1f8bb7a4e69064296f460773170c5435ac
> Author: Colin Ian King <colin.king@canonical.com>
> Date:   Mon May 16 17:22:54 2016 +0100
> 
>     rtc: interface: ignore expired timers when enqueuing new timers
>     
>     commit 2b2f5ff00f63847d95adad6289bd8b05f5983dd5 upstream.
> 
>  8< ---
> 
> The problem does not appear to be in v4.9.x kernels.
> 
> Maybe v4.4.76 is missing one of these?
> http://marc.info/?l=linux-rtc&m=149489307123605&w=2
> Which also includes the commit in question.
> 
> See this thread for more details:
> https://www.linuxquestions.org/questions/slackware-14/slow-hwclock-systohc-on-reboot-shutdown-4175609040/
> 
> Note: I am not the one having this issue. I'm only reporting it, so any
> questions would need to be asked in the above thread. Or perhaps the
> person with the problem will follow this email thread. I will post a
> link to it for them.
> 

I can see a small issue with f0414c1f8bb7a4e69064296f460773170c5435ac
but I'm not sure why it would be hit on v4.4 and not v4.9.

Maybe one has CONFIG_RTC_INTF_DEV_UIE_EMUL and not the other one.

Could you try with the following on top of v4.4.57 (or any other
v4.4.x):

--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -764,7 +764,7 @@ static int rtc_timer_enqueue(struct rtc_device *rtc,
struct rtc_timer *timer)
        }
 
        timerqueue_add(&rtc->timerqueue, &timer->node);
-       if (!next) {
+       if (!next || ktime_before(timer->node.expires, next->expires)) {
                struct rtc_wkalrm alarm;
                int err;
                alarm.time = rtc_ktime_to_tm(timer->node.expires);



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