Whole elapsed seconds are added to secs first, so only the remaining subsecond
ticks should then be subtracted from second_countdown in order to decide whether
secs should be incremented again.
Otherwise, secs is not correctly updated in some cases, typically if the bit 7
of ticks is 1. E.g., with ticks = 128 (i.e. exactly 1 s elapsed) and
second_countdown = 128, secs was first incremented as expected, then 128 was
subtracted from second_countdown, giving 0 and triggering an unwanted second
increment of secs. Or with ticks = 129 (i.e. 1 s + 1 tick) and
second_countdown = 1, secs was first incremented as expected, then 129 was
subtracted from second_countdown, giving 128 and missing a second increment of
secs that should have occurred because second_countdown wrapped around.
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
During PM1+, the hardware timer used to implement the Contiki clock is frozen,
so clock_adjust() needs to be called when exiting those modes in order to
compensate for the clock ticks missed while the timer was frozen. Doing so
changes the Contiki clock time, so etimer_request_poll() needs to be called in
order to inform the etimer library that an etimer might have expired.
Note that waiting for the next clock ISR to call etimer_request_poll() is
unreliable because the system might go back to sleep beforehand.
Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>
