rtcwake doesn't reset wakealarm

[Giacomo <giacomo.perale@gmail.com>]

Hi,

I recently upgraded to util-linux 2.22 and I noticed that powertop started
reporting about 50-60 wakeups per second caused by rtc (interrupt 8). 

I quickly found out that this happened when I used rtcwake to wake up the
machine, and that after the reboot /sys/class/rtc/rtc0/wakealarm was still set
to the scheduled wakeup time (now in the past). Resetting it to 0 with "echo 0 >
/sys/class/rtc/rtc0/wakealarm" made the interrupt stop.

After a quick investigation I discovered that this is caused by commit
1707576155daf644c5df3c1776b52fd297ff9318 ("rtcwake: only invoke RTC_AIE_ON/OFF
ioctls in pairs"): my system uses RTC_WKALM_SET so ioctl_aie_on stays false and
RTC_AIE_OFF doesn't get called.

I removed the check to revert to the previous behaviour and after my machine
rebooted /sys/class/rtc/rtc0/wakealarm was correctly (I suppose) set to 0, rtc
didn't fire regular interrupts anymore and there were apparently no negative
consequences.

Is this a bug or am I missing something?

Thanks,

Giacomo

PS. I'm not subscribed to the list so please cc me if you need other information.