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check always, if sem_post has to wake up a task

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- avoids a (stupid) deadlock
This commit is contained in:
Stefan Lankes 2016-01-16 23:24:30 +01:00
parent ee7d764ba2
commit 078091ef2d
1 changed files with 12 additions and 15 deletions
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27
hermit/include/hermit/semaphore.h
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@ -187,29 +187,26 @@ timeout:
* - -EINVAL on invalid argument
*/
inline static int sem_post(sem_t* s) {
unsigned int k, i;
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
spinlock_irqsave_lock(&s->lock);
if (s->value > 0) {
s->value++;
spinlock_irqsave_unlock(&s->lock);
} else {
unsigned int k, i;
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;
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;
}
spinlock_irqsave_unlock(&s->lock);
i = (i + 1) % MAX_TASKS;
}
spinlock_irqsave_unlock(&s->lock);
return 0;
}