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sys: xtimer: fix some race conditions #4903

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merged 1 commit into from
Mar 11, 2016
Merged

sys: xtimer: fix some race conditions #4903

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5 changes: 1 addition & 4 deletions sys/include/xtimer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -251,11 +251,8 @@ void xtimer_set(xtimer_t *timer, uint32_t offset);
* @note this function runs in O(n) with n being the number of active timers
*
* @param[in] timer ptr to timer structure that will be removed
*
* @return 1 on success
* @return 0 when timer was not active
*/
int xtimer_remove(xtimer_t *timer);
void xtimer_remove(xtimer_t *timer);

/**
* @brief receive a message blocking but with timeout
Expand Down
41 changes: 23 additions & 18 deletions sys/xtimer/xtimer_core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@ static xtimer_t *long_list_head = NULL;
static void _add_timer_to_list(xtimer_t **list_head, xtimer_t *timer);
static void _add_timer_to_long_list(xtimer_t **list_head, xtimer_t *timer);
static void _shoot(xtimer_t *timer);
static void _remove(xtimer_t *timer);
static inline void _lltimer_set(uint32_t target);
static uint32_t _time_left(uint32_t target, uint32_t reference);

Expand Down Expand Up @@ -94,7 +95,10 @@ void _xtimer_set64(xtimer_t *timer, uint32_t offset, uint32_t long_offset)
xtimer_set(timer, (uint32_t) offset);
}
else {
xtimer_remove(timer);
int state = disableIRQ();
if (_is_set(timer)) {
_remove(timer);
}

_xtimer_now64(&timer->target, &timer->long_target);
timer->target += offset;
Expand All @@ -103,7 +107,6 @@ void _xtimer_set64(xtimer_t *timer, uint32_t offset, uint32_t long_offset)
timer->long_target++;
}

int state = disableIRQ();
_add_timer_to_long_list(&long_list_head, timer);
restoreIRQ(state);
DEBUG("xtimer_set64(): added longterm timer (long_target=%" PRIu32 " target=%" PRIu32 ")\n",
Expand Down Expand Up @@ -173,13 +176,17 @@ int _xtimer_set_absolute(xtimer_t *timer, uint32_t target)
return 0;
}

unsigned state = disableIRQ();
if (_is_set(timer)) {
_remove(timer);
}

timer->target = target;
timer->long_target = _long_cnt;
if (target < now) {
timer->long_target++;
}

unsigned state = disableIRQ();
if ( (timer->long_target > _long_cnt) || !_this_high_period(target) ) {
DEBUG("xtimer_set_absolute(): the timer doesn't fit into the low-level timer's mask.\n");
_add_timer_to_long_list(&long_list_head, timer);
Expand Down Expand Up @@ -240,14 +247,8 @@ static int _remove_timer_from_list(xtimer_t **list_head, xtimer_t *timer)
return 0;
}

int xtimer_remove(xtimer_t *timer)
static void _remove(xtimer_t *timer)
{
if (!_is_set(timer)) {
return 0;
}

unsigned state = disableIRQ();
int res = 0;
if (timer_list_head == timer) {
uint32_t next;
timer_list_head = timer->next;
Expand All @@ -261,17 +262,21 @@ int xtimer_remove(xtimer_t *timer)
_lltimer_set(next);
}
else {
res = _remove_timer_from_list(&timer_list_head, timer) ||
_remove_timer_from_list(&overflow_list_head, timer) ||
_remove_timer_from_list(&long_list_head, timer);
if (!_remove_timer_from_list(&timer_list_head, timer)) {
if (!_remove_timer_from_list(&overflow_list_head, timer)) {
_remove_timer_from_list(&long_list_head, timer);
}
}
}
}

timer->target = 0;
timer->long_target = 0;

void xtimer_remove(xtimer_t *timer)
{
int state = disableIRQ();
if (_is_set(timer)) {
_remove(timer);
}
restoreIRQ(state);

return res;
}

static uint32_t _time_left(uint32_t target, uint32_t reference)
Expand Down