C语言中互斥锁与自旋锁及原子操作使用浅析

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#define PTHREAD_NUM	10
#define INFO	printf
pthread_mutex_t mutex;
pthread_spinlock_t spin;
int inc(int *v,int add)
{
	int old;
    //汇编，做一个原子操作
	__asm__ volatile(
		"lock;xaddl %2, %1;"
		:"=a" (old)
		:"m"(*v),"a"(add)
		:"cc","memory"
	);
	return old;
}
void * thread_callback(void *arg)
{
	int *count = (int *)arg;
	int i = 100000;
while(i--)
	{
	#if 0
//互斥锁
		pthread_mutex_lock(&mutex);
		(*count)++;
		pthread_mutex_unlock(&mutex);
	#elif 0
//自旋锁
		pthread_spin_lock(&spin);
		(*count)++;
		pthread_spin_unlock(&spin);
	#else
//原子操作
		inc(count,1);
	#endif
		usleep(1);
	}
}
int main()
{
	pthread_t thread[PTHREAD_NUM] = {0};
	pthread_mutex_init(&mutex,NULL);
	pthread_spin_init(&spin,0);
	int count  = 0;
	for(int i = 0;i<PTHREAD_NUM;i++){
		pthread_create(&thread[i],NULL,thread_callback,&count);
	}
	for(int i = 0;i<100;i++)
	{
		INFO("count == %d\n",count);
		sleep(1);
	}
	return 0;
}

//并发
//互斥锁mutex
//	如果获取不到资源会让出cpu
//	使用场景
//		共享区域执行的内容较多的情况
//自旋锁spinlock
//	如果获取不到资源，会原地自旋，忙等
//	使用场景
//		共享区域执行的内容较少的情况
//原子操作
//	不可分割
//	使用场景
//		做简单++、--操作
//
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <time.h>
#define MAX_PTHREAD 2
#define LOOP_LEN    1000000000
#define LOOP_ADD    10000
int count = 0;
pthread_mutex_t mutex;
pthread_spinlock_t spin;
typedef void *(*functhread)(void *arg);
void do_add(int num)
{
	int sum = 0;
	for(int i = 0;i<num;i++)
	{
		sum +=i;
	}
}
int atomic_add(int *v,int add)
{
	int old;
	__asm__ volatile(
		"lock;xaddl %2, %1;"
		:"=a" (old)
		:"m"(*v),"a"(add)
		:"cc","memory"
	);
	return old;
}
void * atomicthread(void *arg)
{
	for(int i  = 0;i<LOOP_LEN;i++){
		atomic_add(&count,1);
	}
}
void * spinthread(void *arg)
{
	for(int i  = 0;i<LOOP_LEN;i++){
		pthread_spin_lock(&spin);
		count++;
		//do_add(LOOP_ADD);
		pthread_spin_unlock(&spin);
	}
}
void * mutexthread(void *arg)
{
	for(int i  = 0;i<LOOP_LEN;i++){
		pthread_mutex_lock(&mutex);
		count++;
		//do_add(LOOP_ADD);
		pthread_mutex_unlock(&mutex);
	}
}
int test_lock(functhread thre,void * arg)
{
	clock_t start = clock();
	pthread_t tid[MAX_PTHREAD] = {0};
	for(int i = 0;i<MAX_PTHREAD;i++)
	{
	//创建线程
		int ret = pthread_create(&tid[i],NULL,thre,NULL);
		if(0 != ret)
		{
			printf("pthread create rror\n");
			return -1;
		}
	}
	for(int i = 0;i<MAX_PTHREAD;i++){
//回收线程
		pthread_join(tid[i],NULL);
	}
	clock_t end = clock();
	//printf("start  -- %ld\n",start);
	//printf("end  -- %ld\n",end);
	//printf("CLOCKS_PER_SEC  -- %ld\n",CLOCKS_PER_SEC);
	printf("spec lock is  -- %ld\n",(end - start)/CLOCKS_PER_SEC);
}
int main()
{
	pthread_mutex_init(&mutex,NULL);
	pthread_spin_init(&spin,0);
//测试spin
	count = 0;
	printf("use spin ------ \n");
	test_lock(spinthread,NULL);
	printf("count == %d\n",count);
//测试mutex
	count = 0;
	printf("use mutex ------ \n");
	test_lock(mutexthread,NULL);
	printf("count == %d\n",count);
//测试atomic
	count = 0;
	printf("use automic ------ \n");
	test_lock(atomicthread,NULL);
	printf("count == %d\n",count);
	return 0;
}