 1#include 
 2#include 
 3#include 
 4
 5typedef union task {
 6  struct {
 7    const char *name;
 8    union task *next;
 9    void      (*entry)(void *);
10    Context    *context;
11  };
12  uint8_t stack[8192];
13} Task;
14
15Task *current;
16
17void func(void *arg) {
18  while (1) {
19    putch(*(char *)arg);
20    for (int volatile i = 0; i < 100000; i++) ;
21  }
22}
23
24Task tasks[] = {
25  { .name = "a", .entry = func },
26  { .name = "b", .entry = func },
27};
28
29Context *on_interrupt(Event ev, Context *ctx) {
30  if (!current) {
31    current = &tasks[0];
32  } else {
33    current->context = ctx;
34  }
35  return (current = current->next)->context;
36}
37
38int main() {
39  cte_init(on_interrupt);  // call on_interrupt() on traps/interrupts
40
41  for (int i = 0; i < LENGTH(tasks); i++) {
42    Task *task    = &tasks[i];
43    Area stack    = (Area) { &task->context + 1, task + 1 };
44    task->context = kcontext(stack, task->entry, (void *)task->name);
45    task->next    = &tasks[(i + 1) % LENGTH(tasks)];
46  }
47  iset(true);  // Enable external interrupts (timer, I/O, ...)
48  yield();  // Trap
49}
3. 硬件视角的操作系统¶

Take-away Messages¶

课后习题/编程作业¶

1. 编程实践¶
