單生產者+單消費者模式下的雙向循環鏈表之無鎖結構

先貼一段代碼，有時間再來分析：

 

#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>

#define MAX_LEN        10
#define OFF                0x0
#define ON                ~OFF

#define unlikely(x)        __builtin_expect(!!(x), 0)

struct node {
        struct node *pre, *next;
        u_int32_t state;
};

struct _block {
        u_int32_t        insert_index;
        u_int32_t        remove_index;
        struct node list[MAX_LEN];
} block;


void init_list(struct node *list, int num)
{
        int i;
        memset(list, 0, sizeof(*list) * num);
        for(i = 1; i < MAX_LEN - 1; i++) {
                list[i].next = &list[i+1];
                list[i].pre        = &list[i-1];
        }

        list[0].next = &list[1];
        list[0].pre = &list[MAX_LEN - 1];
        list[MAX_LEN - 1].next = &list[0];
        list[MAX_LEN - 1].pre = &list[MAX_LEN - 2];
}



void * producer_func(void *param)
{
        while(1) {
                if(block.insert_index == block.remove_index  \
                        && block.list[block.insert_index].state == ON) {
                        continue;
                }
                block.list[block.insert_index].state = ON;
                if(unlikely(++block.insert_index == MAX_LEN))
                        block.insert_index = 0;
        }
}


void * customer_func(void *param)
{
        while(1) {
                if(block.insert_index == block.remove_index  \
                        && block.list[block.remove_index].state == OFF) {
                        continue;
                }
                block.list[block.remove_index].state = OFF;
                if(unlikely(++block.remove_index == MAX_LEN))
                        block.remove_index = 0;
        }
}


int main(void)
{
        pthread_t tid1, tid2;
        block.insert_index = block.remove_index = 0;
        init_list(block.list, MAX_LEN);


        pthread_create(&tid1, NULL, customer_func, NULL);
        pthread_create(&tid2, NULL, producer_func, NULL);

        while(1)
                sleep(10);
        return 0;
}