1 /*
 2 * linux-3.9.4/mykernel/myinterrupt.c
 3 * 核心自定義啟動程式碼2-定時處理程式和任務排程器
 4 */
 5 
 6 #include <linux/types.h>
 7 #include <linux/string.h>
 8 #include <linux/ctype.h>
 9 #include <linux/tty.h>
10 #include <linux/vmalloc.h>
11 #include "mypcb.h"
12 
13 extern tPCB task[MAX_TASK_NUM];
 
14 extern tPCB* my_current_task;
15 extern volatile int my_need_sched;
16 volatile int time_count = 0;
17 
18 //定時處理程式
19 void my_timer_handler(void)
20 {
21 #if 1
22     if (time_count % 1000 == 0 && my_need_sched != 1)
23     {
24         printk(KERN_NOTICE ">>>my_timer_handler here<<<\n
 
");
25         my_need_sched = 1;
26     }
27     time_count++;
28 #endif
29     return;
30 }
31 
32 //任務排程器
33 void my_schedule(void)
34 {
35     tPCB* next;
36     tPCB* prev;
37     //如果當前任務為空 或 沒有後續任務
38     if (my_current_task == NULL || my_current_task->next == NULL)
39     {
40         return;
41
 
     }
42 
43     printk(KERN_NOTICE ">>>my_shcedule<<\n");
44 
45     //更新任務連結串列指標
46     next = my_current_task->next;
47     prev = my_current_task;
48     //如果任務的狀態表明可執行，則排程
49     if (next->state == 0)  
50     {
51         //儲存當前任務的ebp和esp到stack中
52         //將ebp和esp切換到後續任務
53         __asm__ volatile
54         (
55             "pushl %%ebp\n\t"        /* save current task's base stack address [edp] to stack */
56             "mov1 %%esp, %0\n\t"    /* save esp to prev->thread.sp */
57             "mov1 %2, %%esp\n\t"    /* move next->thread.sp to esp */
58             /* 1f表示在後面的程式碼中搜尋標識為1的程式碼段 */
59             /* 1b標識在前面的程式碼中搜尋標識為1的程式碼段 */
60             /* 數字1可變化 */
61             "mov1 $1f, %1\n\t"        /* save current task's eip to pre->thread.ip, [f] means search label before;[b] means search label behind */
62             "push1 %3,\n\t"            /* switch to next->thread.ip */
63             "ret\n\t"
64             "1:\t"                    /* switch to next process start */
65             "pop1 %%edp\n\t"        /*  */
66             : "=m" (prev->thread.sp), "=m" (prev->thread.ip)
67             : "=m" (next->thread.sp), "=m" (next->thread.ip)
68         );
69 
70         my_current_task = next;
71         printk(KERN_NOTICE ">>>switch %d to %d<<<\n", prev->pid, next->pid);
72     }
73     else //啟動新任務
74     {
75         next->state = 0;
76         my_current_task = next;
77         printk(KERN_NOTICE ">>>switch %d to %d<<<\n", prev->pid, next->pid);
78 
79         //功能同上
80         __asm__ volatile
81         (
82             "push1 %%ebp\n\t"    /* save stack base address [ebp]*/
83             "mov1 %%esp, %0\n\t"    /* save [esp] to prev->thread.sp */
84             "mov1 %2, %%esp\n\t"    /* mov next->thread.sp to [esp] */
85             "mov1 %2, %%ebp\n\t"    /* update [ebp] */
86             "mov1 %1f, %1\n\t"        /* save [eip] to prev->thread.ip */
87             "push1 %3\n\t"            /* save next->thread.ip to [stack] */
88             "ret\n\t"                /* pop next->thead.ip to [eip] */
89             : "=m" (prev->thread.sp), "=m" (prev->thread.ip)
90             : "=m" (next->thread.sp), "=m" (next->thread.ip)
91         );
92 
93         return;
94     }
95 }