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use algorithm with complexity of O(1) to wakeup a task

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This commit is contained in:
Stefan Lankes 2017-10-18 22:24:32 +02:00
parent db365c3634
commit 0e7de04c3d
2 changed files with 25 additions and 24 deletions
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43
include/hermit/semaphore.h
View file

@ -56,14 +56,15 @@ extern "C" {
* - 0 on success
* - -EINVAL on invalid argument
*/
inline static int sem_init(sem_t* s, unsigned int v) {
inline static int sem_init(sem_t* s, unsigned int v)
{
unsigned int i;
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
s->value = v;
s->pos = 0;
s->rpos = s->wpos = 0;
for(i=0; i<MAX_TASKS; i++)
s->queue[i] = MAX_TASKS;
spinlock_irqsave_init(&s->lock);
@ -76,7 +77,8 @@ inline static int sem_init(sem_t* s, unsigned int v) {
* - 0 on success
* - -EINVAL on invalid argument
*/
inline static int sem_destroy(sem_t* s) {
inline static int sem_destroy(sem_t* s)
{
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
@ -94,7 +96,8 @@ inline static int sem_destroy(sem_t* s) {
* - -EINVAL on invalid argument
* - -ECANCELED on failure (You still have to wait)
*/
inline static int sem_trywait(sem_t* s) {
inline static int sem_trywait(sem_t* s)
{
int ret = -ECANCELED;
if (BUILTIN_EXPECT(!s, 0))
@ -114,12 +117,13 @@ inline static int sem_trywait(sem_t* s) {
*
* @param s Address of the according sem_t structure
* @param ms Timeout in milliseconds
* @return
* @return
* - 0 on success
* - -EINVAL on invalid argument
* - -ETIME on timer expired
*/
inline static int sem_wait(sem_t* s, uint32_t ms) {
inline static int sem_wait(sem_t* s, uint32_t ms)
{
task_t* curr_task = per_core(current_task);
if (BUILTIN_EXPECT(!s, 0))
@ -132,8 +136,8 @@ next_try1:
s->value--;
spinlock_irqsave_unlock(&s->lock);
} else {
s->queue[s->pos] = curr_task->id;
s->pos = (s->pos + 1) % MAX_TASKS;
s->queue[s->wpos] = curr_task->id;
s->wpos = (s->wpos + 1) % MAX_TASKS;
block_current_task();
spinlock_irqsave_unlock(&s->lock);
reschedule();
@ -157,8 +161,8 @@ next_try2:
spinlock_irqsave_unlock(&s->lock);
goto timeout;
}
s->queue[s->pos] = curr_task->id;
s->pos = (s->pos + 1) % MAX_TASKS;
s->queue[s->wpos] = curr_task->id;
s->wpos = (s->wpos + 1) % MAX_TASKS;
set_timer(deadline);
spinlock_irqsave_unlock(&s->lock);
reschedule();
@ -181,28 +185,23 @@ timeout:
return 0;
}
/** @brief Give back resource
/** @brief Give back resource
* @return
* - 0 on success
* - -EINVAL on invalid argument
*/
inline static int sem_post(sem_t* s) {
unsigned int k, i;
inline static int sem_post(sem_t* s)
{
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
spinlock_irqsave_lock(&s->lock);
s->value++;
i = s->pos;
for(k=0; k<MAX_TASKS; k++) {
if (s->queue[i] < MAX_TASKS) {
wakeup_task(s->queue[i]);
s->queue[i] = MAX_TASKS;
break;
}
i = (i + 1) % MAX_TASKS;
if (s->queue[s->rpos] < MAX_TASKS) {
wakeup_task(s->queue[s->rpos]);
s->queue[s->rpos] = MAX_TASKS;
s->rpos = (s->rpos + 1) % MAX_TASKS;
}
spinlock_irqsave_unlock(&s->lock);

6
include/hermit/semaphore_types.h
View file

@ -46,8 +46,10 @@ typedef struct sem {
unsigned int value;
/// Queue of waiting tasks
tid_t queue[MAX_TASKS];
/// Position in queue
unsigned int pos;
/// Position in queue to add a task
unsigned int wpos;
/// Position in queue to get a task
unsigned int rpos;
/// Access lock
spinlock_irqsave_t lock;
} sem_t;