Skip to content

sys/xtimer: compare two offsets rather than absolute times [backport 2020.01] #13237

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
aabadie merged 1 commit into from
Jan 30, 2020
Merged

sys/xtimer: compare two offsets rather than absolute times [backport 2020.01] #13237

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
30 changes: 17 additions & 13 deletions sys/xtimer/xtimer_core.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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);
Expand Down Expand Up @@ -93,15 +93,15 @@ 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");
_schedule_earliest_lltimer((uint32_t)now);
}
}
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);
Expand Down Expand Up @@ -148,27 +148,31 @@ 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;
}

/**
* @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);
}

Expand Down Expand Up @@ -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 {
Expand Down