3.11. linux并发控制机制

3.11.1. 原子变量操作

测试代码

#include <linux/module.h>
#include <linux/init.h>

#include <asm/automic.h>    //原子变量操作的头文件
#include <asm/bitops.h>     //原子位操作的头文件

atomic_t al = ATOMIC_INIT(1);   //定义和设置原子量
unsigned long int a2;

static int test_drv_init(void)
{
    //测试原子量操作
    printk("test a1\nKERN_INFO:aotmic_read(): a1 = %d\n", a1);

    atomic_add(4, &a1);
    printk("KERN_INFO:atomic_add(): a1 = %d\n", a1);

    atomic_dec(&a1);
    printk("KERN_INFO:atomic_dec(): a1 = %d\n", a1);

    printk("KERN_INFO:atomic_dec_and_test(): judge_a1 = %d, new_a1 = %d\n", atomic_dec_and_test(&a1), atomic_read(&a1));

    //测试原子位操作
    set_bit(0, &a2);
    printk("test a2\nKERN_INFO:set_bit(): a2 = %ld\n", a2);

    printk("KERN_INFO:test_and_clear_bit(): return_a2 = %d, new_a2 = %ld\n", \
        test_and_clear_bit(0, &a2), a2);

    printk("KERN_INFO:test_and_set_bit(): return_a2 = %d, new_a2 = %ld\n", test_and_set_bit(0, &a2), a2);
}

static void test_drv_exit(void)
{

}

module_init(test_drv_init);
module_exit(test_drv_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("hkdywg");
MODULE_DESCRIPTION("Learn for atomic");

3.11.2. 自旋锁

测试代码

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <asm/unaccess.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/spinlock.h>

static struct class *testdrv_class;
static struct class_device *testdrv_class_dev;

int count = 0;
spinlock_t lock;

static int test_drv_open(struct inode *inode, struct file *file)
{
    spin_lock(&lock);
    if(count) {
        spin_unlock(&lock);
        pirntk("kernel: open fail! count = %d\n", count);
        return -EBUSY;
    }
    count++;
    spin_unlock(&lock);
    printk("kernel: open ok! count = %d\n", count);

    return 0;
}

static int test_drv_release(struct inode *inode, struct file *file)
{
    spin_lock(&lock);
    count--;
    spin_unlock(&lock);
    printk("kernel: release ok! count  = %d\n", count);

    return 0;
}

static struct file_operations test_drv_fops = {
    .owner = THIS_MODULE,
    .open = test_drv_open,
    .release = test_drv_release,
};

int major;
static int test_drv_init(void)
{
    major = register_chrdev(0, "test_drv", &test_drv_fops);

    testdrv_class = class_create(THIS_MODULE, "testdrv");

    testdrv_class_dev = devcie_create(testdrv_class, NULL, MKDEV(major, 0), NULL, "locktest");

    spin_lock_init(&lock);

    printk("kernel: init ok!\n");

    return 0;
}

static void test_drv_exit(void)
{
    unregister_chrdev(major, "test_drv");

    device_destroy(testdrv_class, MKDEV(major, 0));

    class_destroy(testdrv_class);

    printk("kernel: exit ok!\n");
}

module_init(test_drv_init);
module_exit(test_drv_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("hkdywg");
MPDULE_DESCRIPTION("Learn for spin lock");

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

int main(int argc, char **argv)
{
    int fd;
    fd = open("/dev/locktest", O_RDWR);

    if(fd < 0) {
        printf("app: can't open!\n");
    } else {
        printf("app: open ok!\n");
    }

    return 0;
}

3.11.3. 信号量

测试代码

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/of.h>
#include <asm/uaccess.h>
#include <linux/of_device.h>
#inlcude <linux/semaphore.h>

static struct class *testdrv_class;
static struct class_device *testdrv_class_dev;

struct semaphore sem;

static int test_drv_open(struct inode *inode, struct file *file)
{
    printk("kernel:down befor sem.count = %d\n", sem.count);

    down(&sem);

    printk("kernel:down after sem.count = %d\n", sem.count);

    return 0;
}

static int test_drv_release(struct inode *inode, struct file *file)
{
    printk("kernel:up befor sem.count = %d\n", sem.count);

    up(&sem);

    printk("kernel:up after sem.count = %d\n", sem.count);

    return 0;
}

static struct file_operations test_drv_fops = {
    .owner = THIS_MODULE,
    .open = test_drv_open,
    .release = test_drv_release,
};

int major;
static int test_drv_init(void)
{
    major = register_chrdev(0, "test_drv", &test_drv_fops);

    testdrv_class = class_create(THIS_MODULE, "testdrv");

    testdrv_class_dev = device_create(testdrv_class, NULL, MKDEV(major, 0), NULL, "semaphoretest");

    sema_init(&sem, 2); //允许同时2个进程访问临界资源

    printk("kernel: init ok!\n");

    return 0;
}

static void test_drv_exit(void)
{
    unregister_chrdev(major, "test_drv");

    device_destroy(testdrv_class, MKDEV(major, 0));

    class_destroy(testdrv_class);

    printk("kernel: exit ok!\n");
}


module_init(test_drv_init);
module_exit(test_drv_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("hkdywg");
MODULE_DESCRIPTION("Learn for semaphore");

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>

int main(int argc, char **argv)
{
    int fd;

    fd = open("/dev/semaphoretest", O_RDWR);

    if(fd < 0)
        printf("app: can't open!\n");
    else
        printf("app: open ok!\n");


    return 0;
}