1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
/* SPDX-License-Identifier: GPL-2.0-only */
/* This file is part of the coreboot project. */
#include <stddef.h>
#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, unsigned long 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);
}
|
