Suspend: RTC wakeup, sleep
Richard A. Smith
richard at laptop.org
Wed Jul 28 18:39:04 EDT 2010
On 07/28/2010 11:44 AM, Paul Fox wrote:
> > Or if the system wakes up after 50 seconds and doesn't suspend again, my
> > program should run 100 seconds after it started to sleep.
> i'm afraid not. your sleep will be stretched by the duration of
> the suspend. see the following. a 30 second sleep starts at
> 15:42:41. the system suspends for 15 seconds, and wakes (that's
> where the "+r" gets printed) at 15:43:01 (2 seconds later than it
> expected to, btw). the sleep terminates, and prints "sleep
> ended" and the date at 15:43:25. that's roughly 45 seconds after
> the 30 second sleep started.
> [root at xo-a7-2a-c8 dev]# touch /var/run/powerd-inhibit-suspend/1
> [root at xo-a7-2a-c8 dev]# (date; sleep 30; echo sleep ended; date)&
>  3122
> Wed Jul 28 15:42:41 GMT 2010
> [root at xo-a7-2a-c8 dev]# rtcwake -s 15 -m mem; date
> rtcwake: assuming RTC uses UTC ...
> rtcwake: wakeup from "mem" using /dev/rtc0 at Wed Jul 28 15:42:59 2010
> +rWed Jul 28 15:43:01 GMT 2010
> [root at xo-a7-2a-c8 dev]# sleep ended
> Wed Jul 28 15:43:25 GMT 2010
Thanks for the testing. Perhaps we can figure out exactly my problems were.
The above is the way I expected it to work in my original scripts but
for some reason there's a problem with this somewhere. Otherwise I
would have never had to switch to using the RTC time for my delays.
Try your test again and put both of your commands in loops. rtcwake
command in a loop that suspends for a brief period like 1 or 2 seconds
and the sleep start/stop command in something that sends its output to a
log file. Then see if your results are similar.
I think as the sleep time starts to get small and frequent something breaks.
Richard A. Smith <richard at laptop.org>
One Laptop per Child
More information about the Devel