Linux驅動:信號量同步測試

環境：

主機:Fedora12

目標板：MINI6410

目標板LINUX內核版本：2.6.38

信號量主要函數:

//定義信號量

struct semaphore sem;

//初始化信號量

void sema_init(struct semaphore *sem,int val);

//獲得信號量,會導致睡眠,不可在中斷中使用

void down(struct semaphore *sem);

//獲得信號量，能被信號打斷，返回0表示正常返回，返回-EINTR表示被信號打斷

int down_interruptible(struct semaphore *sem);

//嘗試獲得信號量sem,如果能夠立即獲得，返回0,否則返回非0值，它不會導致調用者睡眠,可以在中斷上下文使用

int down_trylock(struct semaphore *sem);

//釋放信號，喚醒等待者

void up(struct semaphore *sem);

測試代碼：

1. #include <linux/miscdevice.h>
2. #include <linux/delay.h>
3. #include <asm/irq.h>
4. //#include <mach/regs-gpio.h>
5. #include <mach/hardware.h>
6. #include <linux/kernel.h>
7. #include <linux/module.h>
8. #include <linux/init.h>
9. #include <linux/mm.h>
10. #include <linux/fs.h>
11. #include <linux/types.h>
12. #include <linux/delay.h>
13. #include <linux/moduleparam.h>
14. #include <linux/slab.h>
15. #include <linux/errno.h>
16. #include <linux/ioctl.h>
17. #include <linux/cdev.h>
18. #include <linux/string.h>
19. #include <linux/list.h>
20. #include <linux/pci.h>
21. #include <asm/uaccess.h>
22. #include <asm/atomic.h>
23. #include <asm/unistd.h>
24. #include <linux/major.h>
26. #include <mach/map.h>
27. #include <mach/regs-clock.h>
28. #include <mach/regs-gpio.h>
30. #include <plat/gpio-cfg.h>
31. #include <mach/gpio-bank-e.h>
32. #include <mach/gpio-bank-k.h>
33. #include <mach/gpio-bank-h.h>
34. #include <mach/gpio-bank-n.h>
35. #include <mach/gpio-bank-l.h>
36. #include <mach/gpio-bank-p.h>
38. #include <linux/device.h>
40. #include <linux/jiffies.h>
42. #define DEVICE_NAME "led_driver"
43. #define T_MAJORS 700
45. static struct cdev fun_cdev;
46. static dev_t dev;
47. static struct class *led_class;
49. struct semaphore sem;
51. //功能：初始化IO
52. static void init_led(void)
53. {
54. unsigned temp;
56. //GPK4-7設置為輸出
57. temp = readl(S3C64XX_GPKCON);
58. temp &= ~((0xf << 4) | (0xf << 5) | (0xf << 6) | (0xf<< 7));
59. temp |= (1 << 16) | (1 << 20) | (1 << 24) | (1 << 28);
60. writel(temp, S3C64XX_GPKCON);
61. }
63. //功能：ioctl操作函數
64. //返回值：成功返回0
65. static long led_driver_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
66. {
67. unsigned int temp = 0;
68. //unsigned long t = 0;
69. wait_queue_head_t wait;
71. //獲取信號量
72. if (down_interruptible(&sem))
73. {
74. return -1;
75. }
77. temp = readl(S3C64XX_GPKDAT);
78. if (cmd == 0)
79. {
80. temp &= ~(1 << (arg + 3));
81. }
82. else
83. {
84. temp |= 1 << (arg + 3);
85. }
87. //等待2S
88. //t = jiffies;
89. //while (time_after(jiffies,t + 2 * HZ) != 1);
90. init_waitqueue_head(&wait);
91. sleep_on_timeout(&wait,2 * HZ);
92. writel(temp,S3C64XX_GPKDAT);
94. printk (DEVICE_NAME"\tjdh:led_driver cmd=%d arg=%d jiffies = %d\n",cmd,arg,jiffies);
96. //釋放信號量
97. up(&sem);
99. return 0;
100. }
102. static struct file_operations io_dev_fops = {
103. .owner = THIS_MODULE,
104. .unlocked_ioctl = led_driver_ioctl,
105. };
107. static int __init dev_init(void)
108. {
109. int ret;
110. unsigned temp;
112. init_led();
114. dev = MKDEV(T_MAJORS,0);
115. cdev_init(&fun_cdev,&io_dev_fops);
116. ret = register_chrdev_region(dev,1,DEVICE_NAME);
117. if (ret < 0) return 0;
118. ret = cdev_add(&fun_cdev,dev,1);
119. if (ret < 0) return 0;
121. printk (DEVICE_NAME"\tjdh:led_driver initialized!!\n");
123. led_class = class_create(THIS_MODULE, "led_class1");
124. if (IS_ERR(led_class))
125. {
126. printk(KERN_INFO "create class error\n");
127. return -1;
128. }
129. device_create(led_class, NULL, dev, NULL, "led_driver");
131. //初始化信號量
132. sema_init(&sem,1);
134. return ret;
135. }
137. static void __exit dev_exit(void)
138. {
139. unregister_chrdev_region(dev,1);
141. device_destroy(led_class, dev);
142. class_destroy(led_class);
143. }
145. module_init(dev_init);
146. module_exit(dev_exit);
147. MODULE_LICENSE("GPL");
148. MODULE_AUTHOR("JDH");

測試

開啟兩個程序，同時打開，雙進程同時操作LED