ionic3 做网站,wordpress制作页面模板,怎么备案域名,如何做一个小程序商城在之前的文章中我们已经了解了RCU机制的原理和Linux的内核源码#xff0c;这里我们要根据RCU机制写一个demo来展示他应该如何使用。
RCU机制的原理 RCU#xff08;全称为Read-Copy-Update#xff09;,它记录所有指向共享数据的指针的使用者#xff0c;当要修改构想数据时这里我们要根据RCU机制写一个demo来展示他应该如何使用。
RCU机制的原理 RCU全称为Read-Copy-Update,它记录所有指向共享数据的指针的使用者当要修改构想数据时首先创建一个副本并在副本中修改所哟访问线程都离开读临界区后使用者的指针指向修改后的副本并且删除旧数据。 他是一种在共享数据结构中实现高效读取和低延迟写入操作的技术。在Linux内核中RCU是一种基于时间窗口的锁机制通过充分利用多核处理器和内存系统的特性在保证并发性的同时提供高性能。
代码示例
#include linux/kernel.h
#include linux/module.h
#include linux/spinlock.h
#include linux/kthread.h
#include linux/delay.h
#include linux/slab.h
#include linux/init.hstruct RCUStruct {int a;struct rcu_head rcu;
};static struct RCUStruct* Global_pointer;static struct task_struct* RCURDThread1, *RCURDThread2, *RCUWTThread;static int RCURDThreadFunc1(void* argc) {struct RCUStruct* pointer NULL;while(1) {msleep(5);rcu_read_lock();mdelay(10);pointer rcu_dereference(Global_pointer);if(pointer)printk(%s : read a %d\n, __func__, pointer-a);rcu_read_unlock();}return 0;
}static int RCURDThreadFunc2(void* argc) {struct RCUStruct* pointer NULL;while(1) {msleep(5);rcu_read_lock();mdelay(10);pointer rcu_dereference(Global_pointer);if(pointer)printk(%s : read a %d\n, __func__, pointer-a);rcu_read_unlock();}return 0;
}static void MyRCUDel(struct rcu_head* rcuh) {struct RCUStruct* p container_of(rcuh, struct RCUStruct, rcu);printk(%s : a %d\n, __func__, p-a);kfree(p);
}static int RCUWTThreadFunc(void* argc) {struct RCUStruct* old_pointer;struct RCUStruct* new_pointer;int value (unsigned long)argc;while(1) {msleep(10);new_pointer kmalloc(sizeof(struct RCUStruct), GFP_KERNEL);old_pointer Global_pointer;*new_pointer *old_pointer;new_pointer-a value;rcu_assign_pointer(Global_pointer, new_pointer);call_rcu(old_pointer-rcu, MyRCUDel);printk(%s : write to new %d\n, __func__, value);value;}return 0;
}static int __init RCUFuncInit(void) {int value 2;printk(Prompt:Successfully initialized the kernel module.\n);Global_pointer kzalloc(sizeof(struct RCUStruct), GFP_KERNEL);RCURDThread1 kthread_run(RCURDThreadFunc1, NULL, RCURD1);RCURDThread2 kthread_run(RCURDThreadFunc2, NULL, RCURD2);RCUWTThread kthread_run(RCUWTThreadFunc, (void*)(unsigned long)value, RCUWT);return 0;
}static void __exit RCUFuncExit(void) {printk(Prompt:Successfully uninstalled kernel module!\n);kthread_stop(RCURDThread1);kthread_stop(RCURDThread2);kthread_stop(RCUWTThread);if(Global_pointer)kfree(Global_pointer);
}module_init(RCUFuncInit);
module_exit(RCUFuncExit);
MODULE_LICENSE(GPL);
MODULE_AUTHOR(lenn louis);Makefile
obj-m:rcu.o CURRENT_PAHT:$(shell pwd)
LINUX_KERNEL:$(shell uname -r) LINUX_KERNEL_PATH:/usr/src/linux-headers-$(LINUX_KERNEL)
all:make -C $(LINUX_KERNEL_PATH) M$(CURRENT_PAHT) modulesclean:make -C $(LINUX_KERNEL_PATH) M$(CURRENT_PAHT) cleals
运行结果
