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sys/xtimer: compare two offsets rather than absolute times

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This commit is contained in:
Hyungsin 2020-01-27 10:17:24 -08:00
parent 142d7b14c0
commit eadd4c9f72
1 changed files with 17 additions and 13 deletions
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30
sys/xtimer/xtimer_core.c
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@ -43,7 +43,7 @@ static xtimer_t *timer_list_head = NULL;
static xtimer_t *long_list_head = NULL;
static bool _lltimer_ongoing = false;
static void _add_timer_to_list(xtimer_t **list_head, xtimer_t *timer);
static void _add_timer_to_list(xtimer_t **list_head, xtimer_t *timer, uint32_t now);
static void _shoot(xtimer_t *timer);
static inline void _update_short_timers(uint64_t *now);
static inline void _update_long_timers(uint64_t *now);
@ -93,7 +93,7 @@ void _xtimer_set64(xtimer_t *timer, uint32_t offset, uint32_t long_offset)
timer->long_start_time = (uint32_t)(now >> 32);
if (!long_offset) {
_add_timer_to_list(&timer_list_head, timer);
_add_timer_to_list(&timer_list_head, timer, (uint32_t)now);
if (timer_list_head == timer) {
DEBUG("_xtimer_set64(): timer is new list head. updating lltimer.\n");
@ -101,7 +101,7 @@ void _xtimer_set64(xtimer_t *timer, uint32_t offset, uint32_t long_offset)
}
}
else {
_add_timer_to_list(&long_list_head, timer);
_add_timer_to_list(&long_list_head, timer, (uint32_t)now);
DEBUG("_xtimer_set64(): added longterm timer.\n");
}
irq_restore(state);
@ -148,17 +148,21 @@ static inline void _schedule_earliest_lltimer(uint32_t now)
/**
* @brief compare two timers. return true if timerA expires earlier than or equal to timerB and false otherwise.
*/
static bool _timer_comparison(xtimer_t* timerA, xtimer_t* timerB)
static bool _timer_comparison(xtimer_t* timerA, xtimer_t* timerB, uint32_t now)
{
if (timerA->long_offset < timerB->long_offset) {
return true;
}
if (timerA->long_offset == timerB->long_offset
/* this condition is needed for when timerA was already expired before timerB starts */
&& (timerA->start_time + timerA->offset < timerB->start_time
/* it is necessary to compare two offsets, instead of two absolute times */
|| timerA->start_time + timerA->offset - timerB->start_time <= timerB->offset)) {
return true;
if (timerA->long_offset == timerB->long_offset) {
uint32_t elapsedA = now - timerA->start_time;
uint32_t elapsedB = now - timerB->start_time;
/* it is necessary to compare two offsets, instead of two absolute times
* two conditions: (1) timerA was already expired
* (2) timerA will expire earlier than or equal to timerB
*/
if (timerA->offset < elapsedA || timerA->offset - elapsedA <= timerB->offset - elapsedB) {
return true;
}
}
return false;
}
@ -166,9 +170,9 @@ static bool _timer_comparison(xtimer_t* timerA, xtimer_t* timerB)
/**
* @brief add a timer to an ordered list of timers
*/
static void _add_timer_to_list(xtimer_t **list_head, xtimer_t *timer)
static void _add_timer_to_list(xtimer_t **list_head, xtimer_t *timer, uint32_t now)
{
while (*list_head && _timer_comparison((*list_head), timer)) {
while (*list_head && _timer_comparison((*list_head), timer, now)) {
list_head = &((*list_head)->next);
}
@ -227,7 +231,7 @@ static inline void _update_long_timers(uint64_t *now)
assert(timer == long_list_head);
_remove_timer_from_list(&long_list_head, timer);
_add_timer_to_list(&timer_list_head, timer);
_add_timer_to_list(&timer_list_head, timer, (uint32_t)*now);
timer = long_list_head;
}
else {