Linux內核線程的創建及在QEMU上的測試方法

一、內核線程的創建

編寫一個字符設備驅動，在驅動注冊時，開啟一個內核線程。在用戶向設備寫入數據時，字符設備的wirte方法能夠激活此內核線程，並在線程中實現打印用戶輸入的數據。

驅動代碼如下（在2.6.22內核上測試通過），關鍵部分加上了注釋：

1. #include <linux/module.h>
2. #include <linux/moduleparam.h>
3. #include <linux/kernel.h> /* printk(), min() */
4. #include <linux/slab.h> /* kmalloc() */
5. #include <linux/fs.h> /* everything... */
6. #include <linux/errno.h> /* error codes */
7. #include <linux/types.h> /* size_t */
8. #include <linux/fcntl.h>
9. #include <linux/cdev.h>
10. #include <asm/uaccess.h>
11. #include <linux/device.h>
12. #include <linux/kthread.h>
13. #include <linux/spinlock.h>
14. static int kthread_major = 0;
15. module_param(kthread_major, int, 0);
16. MODULE_AUTHOR("farsight");
17. MODULE_LICENSE("Dual BSD/GPL");
18. struct kthread_dev {
19. struct task_struct *thread;
20. struct cdev cdev;
21. char* name;
22. int data_size;
23. char data[100];
24. spinlock_t queue_lock;
26. };
27. int kthread_open(struct inode *inode,struct file *filp)
28. {
29. return 0;
30. }
31. ssize_t kthread_read(struct file *file, char __user *buff, size_t count, loff_t *offp)
32. {
33. return 0;
34. }
35. ssize_t kthread_write(struct file *file, const char __user *buff, size_t count, loff_t *offp)
36. {
37. int ret;
38. ret=sizeof(kthread_dev_obj->data);
39. if(count>(ret-1))
40. count=ret-1;
41. if(copy_from_user(kthread_dev_obj->data,buff,count)<0)//獲取用戶數據
42. {
43. goto out1;
44. }
45. spin_lock(&kthread_dev_obj->queue_lock);
46. kthread_dev_obj->data_size=count;
47. spin_unlock(&kthread_dev_obj->queue_lock);
48. wake_up_process(kthread_dev_obj->thread);//喚醒內核線程
49. return count;
50. out1:
51. return 0;
52. }
54. static int kthread_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
55. {
56. return 0;
57. }
59. static int kthread_release(struct inode *node, struct file *file)
60. {
61. return 0;
62. }
64. /*
65. * Set up the cdev structure for a device.
66. */
67. static void kthread_setup_cdev(struct cdev *dev, int minor,
68. struct file_operations *fops)
69. {
70. int err, devno = MKDEV(kthread_major, minor);
72. cdev_init(dev, fops);
73. dev->owner = THIS_MODULE;
74. err = cdev_add (dev, devno, 1);
75. /* Fail gracefully if need be */
76. if (err)
77. printk (KERN_NOTICE "Error %d adding kthread%d", err, minor);
78. }
80. static struct file_operations kthread_remap_ops = {
81. .owner = THIS_MODULE,
82. .open = kthread_open,
83. .release = kthread_release,
84. .read = kthread_read,
85. .write = kthread_write,
86. .ioctl = kthread_ioctl,
87. };
89. static int kthread_fun(void * arg) //內核線程運行函數
90. {
91. while (!kthread_should_stop()) {
92. spin_lock(&kthread_dev_obj->queue_lock);
93. if(kthread_dev_obj->data_size){
94. spin_unlock(&kthread_dev_obj->queue_lock);
95. kthread_dev_obj->data[kthread_dev_obj->data_size]='/0';
96. printk(kthread_dev_obj->data);//打印出用戶空間數據
97. printk("in kthread/n");
98. kthread_dev_obj->data_size=0;
99. }
100. else{
101. set_current_state(TASK_INTERRUPTIBLE);
102. spin_unlock(&kthread_dev_obj->queue_lock);
103. schedule();
104. }
105. }
106. return 0;
107. }
109. static int kthread_init(void)
110. {
111. int result;
112. dev_t dev = MKDEV(kthread_major, 0);
114. /* Figure out our device number. */
115. if (kthread_major)
116. result = register_chrdev_region(dev, 1, "kthread");
117. else {
118. result = alloc_chrdev_region(&dev, 0, 1, "kthread");
119. kthread_major = MAJOR(dev);
120. }
121. if (result < 0) {
122. printk(KERN_WARNING "kthread: unable to get major %d/n", kthread_major);
123. return result;
124. }
125. if (kthread_major == 0)
126. kthread_major = result;
128. kthread_dev_obj= kmalloc(sizeof(struct kthread_dev), GFP_KERNEL);
129. kthread_setup_cdev(&kthread_dev_obj->cdev, 0,&kthread_remap_ops);
130. printk("kthread device installed, with major %d/n", kthread_major);
131. my_class= class_create(THIS_MODULE, "kthread");
132. // device_create(my_class, NULL, MKDEV(kthread_major, 0),NULL, "kthread");
133. device_create(my_class, NULL, MKDEV(kthread_major, 0), "kthread");//for
134. // 2.6.22
135. kthread_dev_obj->name="kthreadtest";//內核線程的名稱
136. spin_lock_init(&kthread_dev_obj->queue_lock);
137. kthread_dev_obj->thread=kthread_run(kthread_fun,kthread_dev_obj,"%sd",kthread_dev_obj->name);//創建並運行內核線程
138. return 0;
139. }
140. static void kthread_cleanup(void)
141. {
142. kthread_stop(kthread_dev_obj->thread);//停止內核線程
143. cdev_del(&kthread_dev_obj->cdev);
144. unregister_chrdev_region(MKDEV(kthread_major, 0), 1);
145. device_destroy(my_class,MKDEV(kthread_major,0));
146. class_destroy(my_class);
147. kfree(kthread_dev_obj);
148. printk("kthread device uninstalled/n");
149. }
150. module_init(kthread_init);
151. module_exit(kthread_cleanup);

二、在QEMU平台上的測試方法

QEMU可以模擬很多硬件平台，使用QEMU適用於你手邊沒用硬件平台，或沒用很好的內核調試工具的情況。

這裡主要介紹使用QEMU模擬ARM開發環境，並運行linux系統的過程。

1、系統環境

操作系統平台：Ubuntu 10.10

交叉工具：arm-softfloat-linux-gnu

測試內核：Linux2.6.22

測試平台：RealView-EB （QEMU 模擬）

2、安裝QEMU的方法

使用新立得獲取安裝包