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
183
184
185
186
187
188
189
|
#include <task.h>
#include <kmalloc.h>
#include <dbglog.h>
#include <idt.h>
#include <frame.h>
#include <paging.h>
void save_context_and_enter_scheduler(saved_context_t *ctx);
void resume_context(saved_context_t *ctx);
task_t *current_task = 0;
// ====================== //
// THE PROGRAMMABLE TIMER //
// ====================== //
void set_pit_frequency(uint32_t freq) {
uint32_t divisor = 1193180 / freq;
ASSERT(divisor < 65536); // must fit on 16 bits
uint8_t l = (divisor & 0xFF);
uint8_t h = ((divisor >> 8) & 0xFF);
outb(0x43, 0x36);
outb(0x40, l);
outb(0x40, h);
}
// ================== //
// THE TASK SCHEDULER //
// ================== //
static task_t *queue_first_task = 0, *queue_last_task = 0;
void enqueue_task(task_t *t, bool just_ran) {
ASSERT(t->state == T_STATE_RUNNING);
if (queue_first_task == 0) {
queue_first_task = queue_last_task = t;
t->next_in_queue = 0;
} else if (just_ran) {
t->next_in_queue = 0;
queue_last_task->next_in_queue = t;
queue_last_task = t;
} else {
t->next_in_queue = queue_first_task;
queue_first_task = t;
}
}
task_t* dequeue_task() {
task_t *t = queue_first_task;
if (t == 0) return 0;
queue_first_task = t->next_in_queue;
if (queue_first_task == 0) queue_last_task = 0;
return t;
}
// ================ //
// THE TASKING CODE //
// ================ //
void run_scheduler() {
// This function is expected NEVER TO RETURN
if (current_task != 0 && current_task->state == T_STATE_RUNNING) {
enqueue_task(current_task, true);
}
current_task = dequeue_task();
if (current_task != 0) {
resume_context(¤t_task->ctx);
} else {
// Wait for an IRQ
asm volatile("sti; hlt");
// At this point an IRQ has happenned
// and has been processed. Loop around.
run_scheduler();
ASSERT(false);
}
}
static void run_task(void (*entry)(void*)) {
ASSERT(current_task->state == T_STATE_RUNNING);
ASSERT(current_task->has_result);
current_task->has_result = false;
asm volatile("sti");
entry(current_task->result);
current_task->state = T_STATE_FINISHED;
// TODO : add job for deleting the task, or whatever
yield(); // expected never to return!
ASSERT(false);
}
task_t *new_task(entry_t entry) {
task_t *t = (task_t*)kmalloc(sizeof(task_t));
if (t == 0) return 0;
void* stack = region_alloc(KPROC_STACK_SIZE, REGION_T_KPROC_STACK, 0);
if (stack == 0) {
kfree(t);
return 0;
}
for (void* i = stack + PAGE_SIZE; i < stack + KPROC_STACK_SIZE; i += PAGE_SIZE) {
uint32_t f = frame_alloc(1);
if (f == 0) {
region_free_unmap_free(stack);
kfree(t);
return 0;
}
pd_map_page(i, f, true);
}
t->stack_region = find_region(stack);
t->ctx.esp = (uint32_t*)(t->stack_region->addr + t->stack_region->size);
*(--t->ctx.esp) = (uint32_t)entry; // push first argument : entry point
*(--t->ctx.esp) = 0; // push invalid return address (the run_task function never returns)
t->ctx.eip = (void(*)())run_task;
t->state = T_STATE_WAITING;
t->result = 0;
t->has_result = false;
t->more_data = 0;
return t;
}
void tasking_setup(entry_t cont, void* arg) {
set_pit_frequency(100);
idt_set_irq_handler(IRQ0, yield);
task_t *t = new_task(cont);
ASSERT(t != 0);
resume_with_result(t, arg, false);
run_scheduler(); // never returns
ASSERT(false);
}
void yield() {
if (current_task == 0) {
// might happen before tasking is initialized
dbg_printf("Warning: probable deadlock.");
} else {
save_context_and_enter_scheduler(¤t_task->ctx);
}
}
void* wait_for_result() {
uint32_t eflags;
asm volatile("pushf; pop %0" : "=r"(eflags));
asm volatile("cli");
if (!current_task->has_result) {
current_task->state = T_STATE_WAITING;
save_context_and_enter_scheduler(¤t_task->ctx);
}
ASSERT(current_task->has_result);
current_task->has_result = false;
if (eflags & EFLAGS_IF) asm volatile("sti");
return current_task->result;
}
void resume_with_result(task_t *task, void* data, bool run_at_once) {
uint32_t eflags;
asm volatile("pushf; pop %0" : "=r"(eflags));
asm volatile("cli");
task->has_result = true;
task->result = data;
if (task->state == T_STATE_WAITING) {
task->state = T_STATE_RUNNING;
enqueue_task(task, false);
}
if (run_at_once) yield();
if (eflags & EFLAGS_IF) asm volatile("sti");
}
/* vim: set ts=4 sw=4 tw=0 noet :*/
|
