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kernel: sched: fix empty list detection

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CONTAINER_OF() on a NULL pointer returns some offset around NULL and not
another NULL pointer.  We have to check for that ourselves.

This only worked because the dnode happened to be at the start of the
struct.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
This commit is contained in:
Peter A. Bigot 2019-01-03 23:36:28 -06:00 • committed by Carles Cufí
commit 692e1033e7
1 changed files with 15 additions and 3 deletions
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18
kernel/sched.c
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@ -591,9 +591,13 @@ void _priq_dumb_remove(sys_dlist_t *pq, struct k_thread *thread)
struct k_thread *_priq_dumb_best(sys_dlist_t *pq)
{
struct k_thread *t = NULL;
sys_dnode_t *n = sys_dlist_peek_head(pq);
return CONTAINER_OF(n, struct k_thread, base.qnode_dlist);
if (n != NULL) {
t = CONTAINER_OF(n, struct k_thread, base.qnode_dlist);
}
return t;
}
bool _priq_rb_lessthan(struct rbnode *a, struct rbnode *b)
@ -648,9 +652,13 @@ void _priq_rb_remove(struct _priq_rb *pq, struct k_thread *thread)
struct k_thread *_priq_rb_best(struct _priq_rb *pq)
{
struct k_thread *t = NULL;
struct rbnode *n = rb_get_min(&pq->tree);
return CONTAINER_OF(n, struct k_thread, base.qnode_rb);
if (n != NULL) {
t = CONTAINER_OF(n, struct k_thread, base.qnode_rb);
}
return t;
}
#ifdef CONFIG_SCHED_MULTIQ
@ -683,10 +691,14 @@ struct k_thread *_priq_mq_best(struct _priq_mq *pq)
return NULL;
}
struct k_thread *t = NULL;
sys_dlist_t *l = &pq->queues[__builtin_ctz(pq->bitmask)];
sys_dnode_t *n = sys_dlist_peek_head(l);
return CONTAINER_OF(n, struct k_thread, base.qnode_dlist);
if (n != NULL) {
t = CONTAINER_OF(n, struct k_thread, base.qnode_dlist);
}
return t;
}
int _unpend_all(_wait_q_t *wait_q)