单链表有锁队列实现

[root@TEST comm_queue]# cat queue.h

#ifndef MP4_QUEUE_H
#define MP4_QUEUE_H
#include <assert.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>

typedef enum {
        QUEUE_EMPTY,
        QUEUE_REGULAR
} queue_flag;

typedef struct _qnode_t qnode_t;
struct _qnode_t {
    int fd;
    qnode_t *next;
};

typedef struct _queue_t queue_t;
struct _queue_t {
    qnode_t *head;
    qnode_t *tail;
};

//extern queue_t queue;
extern queue_flag queue_test(queue_t *queue);
extern void enqueue(queue_t *queue, int fd);
extern int  dequeue(queue_t *queue);
extern void traverse(queue_t *q);
#endif

[root@TEST_190 comm_queue]# cat queue.c

#include "queue.h"

queue_flag queue_test(queue_t *queue)
{
    assert(queue);
    if (queue->head == NULL)
        return QUEUE_EMPTY;
    return QUEUE_REGULAR;
}

void enqueue(queue_t *queue,int fd)
{
    assert(queue);
    qnode_t *node = NULL;
    node = (qnode_t*)malloc(sizeof(qnode_t));
    if (!node) {
        perror("enqueue malloc error:\n");
        return;
    }
    node->fd = fd;
    node->next = NULL;
    if (queue->tail == NULL) {
        queue->head = queue->tail = node;
        return;
    }
    queue->tail->next = node;
    queue->tail = node;
}

int dequeue(queue_t *queue)
{
    assert(queue);
    if (queue->tail == NULL && queue->head == NULL) {
        //printf("dequeue() queue is empty!\n");
        return -1;
    }
    qnode_t *tmp = NULL;
    int ret = -1;
    tmp = queue->head;
    ret = tmp->fd;
    queue->head = tmp->next;
    //如果出对到队尾了，需要将队尾更新为空,以便于后续再次执行入对操作
    if (queue->tail == tmp)
        queue->tail = queue->tail->next;
    free(tmp);
    return ret;
}

void traverse(queue_t *q)
{
    unsigned long pid = pthread_self();
    if (q->head == NULL) {
        printf("traverse() {%d} queue is empty!\n",pid);
        return;
    }

    qnode_t *pos = NULL;
    int i = 0;
    for (pos = q->head;pos != NULL; pos = pos->next,i++) {
        printf("traverse{%lu} pos[%d]=%d\n",pid,i,pos->fd);
    }
}

验证程序
[root@TEST_190 comm_queue]# cat main.c

#include "queue.h"

int count = 10000;
pthread_mutex_t m;
queue_t queue = {NULL, NULL};
void *writer_thread(void *param);
void *reader_thread(void *param);

int main(void)
{
    struct timeval start,end;
    gettimeofday(&start, NULL);
    pthread_t writer,reader;
    pthread_mutex_init(&m, NULL);
    pthread_create(&writer, NULL, writer_thread, NULL);
    pthread_create(&reader, NULL, reader_thread, NULL);

    pthread_join(writer, NULL);
    pthread_join(reader, NULL);
    gettimeofday(&end, NULL);
    double elasp = (end.tv_sec - start.tv_sec) * 1000000.0 + (end.tv_usec - start.tv_usec);
    printf("pthread id = %lu, elasp = %f\n", pthread_self(), elasp);
    //traverse(&queue);
    return 0;
}

void *writer_thread(void *param)
{
    int i;
    for (i = 0; i < count; i++ ) {
        pthread_mutex_lock(&m);
        enqueue(&queue,i);
        printf("enqueue [%d]\n",i);
        pthread_mutex_unlock(&m);
    }
    //traverse(&queue);
}

void *reader_thread(void *param)
{
    int ret=0,i;
    //模拟无限出队的情况，暂时执行次数为 100*count
    for(i=0;i<100*count;i++) {
        pthread_mutex_lock(&m);
        ret = dequeue(&queue);
        if (ret == -1) {
            printf(".");
        } else {
            printf("dequeue ret = %d\n",ret);
        }

        pthread_mutex_unlock(&m);
    }
    //traverse(&queue);
}

编译和确认，需要查看log确认，队列为空时的出队操作，会打出“.”：

gcc queue.c main.c -o q1 -g  -lpthread
./q1 | tee log