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28
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1 /* Scheduler functions */
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2
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25
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3 #include "kernel.h"
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4
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5 // global variables:
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6 uint64_t next_pid = 1;
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7 task_t* ready_queue = 0; // Head of the queue of tasks.
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8 task_t* current_task = 0; // Pointer to the currently running task.
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9
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10 void initialize_tasking()
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11 {
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12 next_pid = 1;
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13 }
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14
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15 /*
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16 Create a new task with some loaded program.
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17 */
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18 void new_task()
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19 {
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20 task_t* newtask = (task_t*)kmalloc(sizeof(task_t));
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21 newtask->pid = next_pid++;
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22 newtask->rip = 0;
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23 newtask->next = 0;
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24
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25 // Append the new task to the ready queue:
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26 task_t* task = ready_queue;
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27 while (task->next != 0)
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28 {
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29 task = task->next;
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30 }
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31 task->next = newtask;
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32 }
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33
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34 /* Fork function duplicates the process */
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35 void task_fork()
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36 {
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37 asm volatile("cli"); // Disable interrupts
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38 task_t *parent_task = current_task;
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39
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40 // Create new task:
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41 task_t *new_task = (task_t*)kmalloc(sizeof(task_t));
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42 new_task->pid = next_pid++;
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43 new_task->rsp = 0;
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44 new_task->rbp = 0;
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45 new_task->rip = 0;
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46 new_task->next = 0;
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47
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48 // Append to the queue:
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49 task_t* tmp_task = ready_queue;
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50 while (tmp_task->next != 0)
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51 {
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52 tmp_task = tmp_task->next;
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53 }
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54 tmp_task->next = new_task;
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55
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56 uint64_t rip = read_rip();
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57
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58 if (current_task == parent_task)
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59 {
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60 uint64_t rbp, rsp;
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61 asm volatile("mov %%rsp, %0" : "=r"(rsp));
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62 asm volatile("mov %%rbp, %0" : "=r"(rbp));
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63 new_task->rip = rip;
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64
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65 asm volatile("sti");
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66 }
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67 }
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68
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69 /*
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70 Scheduler function that switches tasks for multi tasking.
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71 */
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72 void task_scheduler()
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73 {
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74 if (current_task == 0)
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75 {
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76 return;
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77 }
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78
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79 uint64_t rbp, rsp, rip;
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80
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81 rip = 0;
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82 rsp = 0;
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83 rbp = 0;
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84
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85 current_task->rip = rip; // TODO
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86 current_task->rsp = rsp;
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87 current_task->rbp = rbp;
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88
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89 // Select next task:
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90 current_task = current_task->next;
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91 if (current_task == 0)
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92 {
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93 current_task = ready_queue;
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94 }
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95
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96 // Set the rbp, rsp and rip registers:
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97 rsp = current_task->rsp;
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98 rbp = current_task->rbp;
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99 }
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100
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