深圳 做公司网站,网站用什么建设,怎么在阿里云建立网站,制作相册怎么做自旋锁#xff08;spinlock#xff09; 更多内容可以查看我的github 概念
Spinlock是linux内核中常用的一种互斥锁机制#xff0c;和mutex不同#xff0c;当无法持锁进入临界区的时候#xff0c;当前执行线索不会阻塞#xff0c;而是不断的自旋等待该锁释放。 正因为如此…自旋锁spinlock 更多内容可以查看我的github 概念
Spinlock是linux内核中常用的一种互斥锁机制和mutex不同当无法持锁进入临界区的时候当前执行线索不会阻塞而是不断的自旋等待该锁释放。 正因为如此自旋锁也是可以用在中断上下文的。 也正是因为自旋临界区的代码要求尽量的精简否则在高竞争场景下会浪费宝贵的CPU资源。
使用
#include linux/spinlock.h
// 定义自选锁
spinlock_t lock;
// 初始化自旋锁
spin_lock_init(lock);
// 获取自旋锁
spin_lock(lock);
// 释放自旋锁
spin_unlock(lock);尽管使用自旋锁可以保证临界区不受别的CPU和本CPU内的抢占进程打扰。但是得到锁的代码路径在执行临界区的时候可能受到 中断 的影响。因此需要使用自旋锁的衍生函数。
// 锁 开/关中断
spin_lock_irq();
spin_unlock_irq();// 锁 关中断并保存中断状态/开中断并恢复中断状态
spin_lock_irqsave();
spin_unlock_irqrestore();测试
make
dmesg -C
insmod spinlock.ko
mknod /dev/spinlock c 232 0cat /dev/spinlock
dmesg
echo 1 /dev/spinlock
dmesg
cat /dev/spinlock
dmesg代码
/** Date: 2024-04-30 15:35:19* author: lidonghang-02 2426971102qq.com* LastEditTime: 2024-05-19 20:02:50*/
#include linux/module.h
#include linux/kernel.h
#include linux/fs.h
#include linux/cdev.h
#include linux/slab.h
#include linux/spinlock.h
#include linux/uaccess.h
#include linux/device.h#define DEVICE_NAME spinlock_dev#define SPINLOCK_MAJOR 0
static int spinlock_major SPINLOCK_MAJOR;struct spinlock_dev
{struct cdev cdev;int shared_resource;struct device *class_dev;
};struct spinlock_dev *spinlock_devp;
struct class *my_class NULL;
static dev_t dev_no;// 自旋锁
spinlock_t my_lock;static int spinlock_open_func(struct inode *inode, struct file *file)
{file-private_data spinlock_devp;printk(KERN_INFO Spinlock Device Opened\n);return 0;
}
static int spinlock_release_func(struct inode *inode, struct file *file)
{printk(KERN_INFO Spinlock Device Closed\n);return 0;
}
static ssize_t spinlock_read_func(struct file *filp, char __user *buf, size_t size,loff_t *ppos)
{struct spinlock_dev *dev filp-private_data;// 从用户空间读取数据if (copy_to_user(buf, dev-shared_resource, sizeof(int))){printk(KERN_ERR Failed to copy data to user space\n);return -EFAULT;}elseprintk(KERN_INFO shared_resource: %d\n, dev-shared_resource);ppos sizeof(int);return 0;
}
static ssize_t spinlock_write_func(struct file *filp, const char __user *buf, size_t size,loff_t *ppos)
{unsigned long flags;unsigned int count size;struct spinlock_dev *dev filp-private_data;// 加锁spin_lock_irqsave(my_lock, flags);// 假设的共享资源操作dev-shared_resource 1;// 解锁spin_unlock_irqrestore(my_lock, flags);printk(KERN_INFO shared_resource: %d\n, dev-shared_resource);return count;
}// 设备操作结构体
static const struct file_operations fops {.open spinlock_open_func,.release spinlock_release_func,.read spinlock_read_func,.write spinlock_write_func,
};// 驱动初始化函数
static int __init my_driver_init_module(void)
{int ret;dev_no MKDEV(spinlock_major, 0);spin_lock_init(my_lock);// 分配设备号if (spinlock_major)ret register_chrdev_region(dev_no, 1, DEVICE_NAME);else{ret alloc_chrdev_region(dev_no, 0, 1, DEVICE_NAME);spinlock_major MAJOR(dev_no);}if (ret 0){printk(KERN_ERR Failed to allocate device number\n);return ret;}spinlock_devp kzalloc(sizeof(struct spinlock_dev), GFP_KERNEL);if (!spinlock_devp){ret -ENOMEM;goto free_chrdev_region;}my_class class_create(THIS_MODULE, spinlock);if (IS_ERR(my_class)){ret PTR_ERR(my_class);goto free_chrdev_region;}// 初始化字符设备cdev_init(spinlock_devp-cdev, fops);spinlock_devp-cdev.owner THIS_MODULE;ret cdev_add(spinlock_devp-cdev, dev_no, 1);if (ret 0){printk(KERN_ERR Failed to add cdev\n);goto free_chrdev_class;}spinlock_devp-class_dev device_create(my_class, NULL, dev_no, NULL, DEVICE_NAME);if (IS_ERR(spinlock_devp-class_dev)){ret PTR_ERR(spinlock_devp-class_dev);goto free_chrdev_class;}printk(KERN_INFO My Spinlock Driver Init\n);return 0;free_chrdev_class:class_destroy(my_class);free_chrdev_region:unregister_chrdev_region(dev_no, 1);return ret;
}// 驱动退出函数
static void __exit my_driver_exit_module(void)
{cdev_del(spinlock_devp-cdev);unregister_chrdev_region(dev_no, 1);kfree(spinlock_devp);printk(KERN_INFO My Spinlock Driver Exited\n);
}module_init(my_driver_init_module);
module_exit(my_driver_exit_module);MODULE_AUTHOR(lidonghang-02);
MODULE_LICENSE(GPL);
