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/* SPDX-License-Identifier: GPL-2.0-only */
#include <timer.h>
#define MAX_TIMER_QUEUE_ENTRIES 64
/* The timer queue is implemented using a min heap. Therefore the first
* element is the one with smallest time to expiration. */
struct timer_queue {
int num_entries;
int max_entries;
struct timeout_callback *queue[MAX_TIMER_QUEUE_ENTRIES];
};
static struct timer_queue global_timer_queue = {
.num_entries = 0,
.max_entries = MAX_TIMER_QUEUE_ENTRIES,
.queue = { 0 },
};
static inline int timer_queue_empty(struct timer_queue *tq)
{
return tq->num_entries == 0;
}
static inline int timer_queue_full(struct timer_queue *tq)
{
return tq->num_entries == tq->max_entries;
}
static inline struct timeout_callback *timer_queue_head(struct timer_queue *tq)
{
if (timer_queue_empty(tq))
return NULL;
return tq->queue[0];
}
static int timer_queue_insert(struct timer_queue *tq,
struct timeout_callback *tocb)
{
int index;
/* No more slots. */
if (timer_queue_full(tq))
return -1;
index = tq->num_entries;
tq->num_entries++;
tq->queue[index] = tocb;
while (index != 0) {
struct timeout_callback *parent;
int parent_index;
parent_index = (index - 1) / 2;
parent = tq->queue[parent_index];
/* All other ancestors are less than or equal to the current. */
if (mono_time_cmp(&parent->expiration, &tocb->expiration) <= 0)
break;
/* The parent is greater than current. Swap them. */
tq->queue[parent_index] = tocb;
tq->queue[index] = parent;
index = parent_index;
}
return 0;
}
/* Get the index containing the entry with smallest value. */
static int timer_queue_min_child_index(struct timer_queue *tq, int index)
{
int left_child_index;
int right_child_index;
left_child_index = 2 * index + 1;
if (left_child_index >= tq->num_entries)
return -1;
right_child_index = left_child_index + 1;
if (right_child_index >= tq->num_entries)
return left_child_index;
if (mono_time_cmp(&tq->queue[left_child_index]->expiration,
&tq->queue[right_child_index]->expiration) < 0) {
return left_child_index;
}
return right_child_index;
}
static void timer_queue_remove_head(struct timer_queue *tq)
{
int index;
struct timeout_callback *tocb;
/* In order to remove the head the deepest child is replaced in the
* head slot and bubbled down the tree. */
tq->num_entries--;
tocb = tq->queue[tq->num_entries];
tq->queue[0] = tocb;
index = 0;
while (1) {
int min_child_index;
struct timeout_callback *child;
min_child_index = timer_queue_min_child_index(tq, index);
/* No more entries to compare against. */
if (min_child_index < 0)
break;
child = tq->queue[min_child_index];
/* Current index is the correct place since it is smaller or
* equal to the smallest child. */
if (mono_time_cmp(&tocb->expiration, &child->expiration) <= 0)
break;
/* Need to swap with smallest child. */
tq->queue[min_child_index] = tocb;
tq->queue[index] = child;
index = min_child_index;
}
}
static struct timeout_callback *
timer_queue_expired(struct timer_queue *tq, struct mono_time *current_time)
{
struct timeout_callback *tocb;
tocb = timer_queue_head(tq);
if (tocb == NULL)
return NULL;
/* The timeout callback hasn't expired yet. */
if (mono_time_before(current_time, &tocb->expiration))
return NULL;
timer_queue_remove_head(tq);
return tocb;
}
int timer_sched_callback(struct timeout_callback *tocb, uint64_t us)
{
struct mono_time current_time;
if ((long)us < 0)
return -1;
timer_monotonic_get(¤t_time);
tocb->expiration = current_time;
mono_time_add_usecs(&tocb->expiration, us);
/* The expiration overflowed. */
if (us != 0 && !mono_time_before(¤t_time, &tocb->expiration))
return -1;
return timer_queue_insert(&global_timer_queue, tocb);
}
int timers_run(void)
{
struct timeout_callback *tocb;
struct mono_time current_time;
timer_monotonic_get(¤t_time);
tocb = timer_queue_expired(&global_timer_queue, ¤t_time);
if (tocb != NULL)
tocb->callback(tocb);
return !timer_queue_empty(&global_timer_queue);
}
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