多个生产者，单个消费者，只考虑生产者之间的同步互斥
#include "unpipc.h"#define MAXNITEMS 1000000#define MAXNTHREADS 100
int nitems; /**//* read-only by producer and consumer */struct 
{
pthread_mutex_t mutex; //互斥信号量 int buff[MAXNITEMS]; int nput;//下一个存放元素的下标 int nval;//下一个存放的值} shared = { PTHREAD_MUTEX_INITIALIZER };void *produce(void *), *consume(void *);intmain(int argc, char **argv){ int i, nthreads, count[MAXNTHREADS]; pthread_t tid_produce[MAXNTHREADS], tid_consume; if (argc != 3) err_quit("usage: prodcons2 <#items> <#threads>"); nitems = min(atoi(argv[1]), MAXNITEMS);//生产者存放的条目数 nthreads = min(atoi(argv[2]), MAXNTHREADS);//待创建的生产者线程数 Set_concurrency(nthreads);//通知线程系统我们希望并发多少线程
/**//* 4start all the producer threads */ for (i = 0; i < nthreads; i++) { count[i] = 0;//计数器初始化为0 Pthread_create(&tid_produce[i], NULL, produce, &count[i]);//创建生产者线程
} /**//* 4wait for all the producer threads */ for (i = 0; i < nthreads; i++) { Pthread_join(tid_produce[i], NULL);//等待生产者线程结束 printf("count[%d] = %d\n", i, count[i]); } //这样做的目的是为了避免生产者和消费者之间的同步问题，这里只考虑生产者之间的同步 /**//* 4start, then wait for the consumer thread */ Pthread_create(&tid_consume, NULL, consume, NULL);//创建消费者线程 Pthread_join(tid_consume, NULL); exit(0);
}/**//* end main *//**//* include producer */void *produce(void *arg){ for ( ; ; ) { Pthread_mutex_lock(&shared.mutex); if (shared.nput >= nitems) {//生产完毕 Pthread_mutex_unlock(&shared.mutex); return(NULL); /**//* array is full, we're done */ } shared.buff[shared.nput] = shared.nval; shared.nput++; shared.nval++; Pthread_mutex_unlock(&shared.mutex); *((int *) arg) += 1;//每个线程私有的计数器，不需要加锁 }}void *consume(void *arg){ int i; for (i = 0; i < nitems; i++) { if (shared.buff[i] != i) printf("buff[%d] = %d\n", i, shared.buff[i]); } return(NULL);}/**//* end producer */
生产者和消费者之间的同步，消费者采用的方式就是不断轮询。
#include "unpipc.h"#define MAXNITEMS 1000000#define MAXNTHREADS 100int nitems; /**//* read-only by producer and consumer */struct { pthread_mutex_t mutex; int buff[MAXNITEMS]; int nput; int nval;} shared = { PTHREAD_MUTEX_INITIALIZER };void *produce(void *), *consume(void *);/**//* include main */intmain(int argc, char **argv){ int i, nthreads, count[MAXNTHREADS]; pthread_t tid_produce[MAXNTHREADS], tid_consume; if (argc != 3) err_quit("usage: prodcons3 <#items> <#threads>"); nitems = min(atoi(argv[1]), MAXNITEMS); nthreads = min(atoi(argv[2]), MAXNTHREADS); /**//* 4create all producers and one consumer */ Set_concurrency(nthreads + 1); for (i = 0; i < nthreads; i++) { count[i] = 0; Pthread_create(&tid_produce[i], NULL, produce, &count[i]); } Pthread_create(&tid_consume, NULL, consume, NULL); /**//* 4wait for all producers and the consumer */ for (i = 0; i < nthreads; i++) { Pthread_join(tid_produce[i], NULL); printf("count[%d] = %d\n", i, count[i]); } Pthread_join(tid_consume, NULL); exit(0);}/**//* end main */void *produce(void *arg){ for ( ; ; ) { Pthread_mutex_lock(&shared.mutex); if (shared.nput >= nitems) { Pthread_mutex_unlock(&shared.mutex); return(NULL); /**//* array is full, we're done */ } shared.buff[shared.nput] = shared.nval; shared.nput++; shared.nval++; Pthread_mutex_unlock(&shared.mutex); *((int *) arg) += 1; }}/**//* include consume */voidconsume_wait(int i){ for ( ; ; ) { Pthread_mutex_lock(&shared.mutex); if (i < shared.nput) { Pthread_mutex_unlock(&shared.mutex); return; /**//* an item is ready */ } Pthread_mutex_unlock(&shared.mutex); }}void *consume(void *arg){ int i; for (i = 0; i < nitems; i++) { consume_wait(i); if (shared.buff[i] != i) printf("buff[%d] = %d\n", i, shared.buff[i]); } return(NULL);}/**//* end consume */
每个条件变量都有一个互斥锁与之关联，调用pthread_cond_wait等待某个条件为真时，同时指定其条件变量的地址和所关联的互斥锁的地址
使用条件变量来通知，避免消费者轮询
/**//* include globals */#include "unpipc.h"#define MAXNITEMS 1000000#define MAXNTHREADS 100 /**//* globals shared by threads */int nitems; /**//* read-only by producer and consumer */int buff[MAXNITEMS];struct {//用于生产者之间的同步 pthread_mutex_t mutex; int nput; /**//* next index to store */ int nval; /**//* next value to store */} put = { PTHREAD_MUTEX_INITIALIZER };struct {//用于生产者和消费者之间同步 pthread_mutex_t mutex; pthread_cond_t cond; int nready; /**//* number ready for consumer */} nready = { PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER };/**//* end globals */void *produce(void *), *consume(void *);/**//* include main */intmain(int argc, char **argv){ int i, nthreads, count[MAXNTHREADS]; pthread_t tid_produce[MAXNTHREADS], tid_consume; if (argc != 3) err_quit("usage: prodcons6 <#items> <#threads>"); nitems = min(atoi(argv[1]), MAXNITEMS); nthreads = min(atoi(argv[2]), MAXNTHREADS); Set_concurrency(nthreads + 1); /**//* 4create all producers and one consumer */ for (i = 0; i < nthreads; i++) { count[i] = 0; Pthread_create(&tid_produce[i], NULL, produce, &count[i]); } Pthread_create(&tid_consume, NULL, consume, NULL); /**//* wait for all producers and the consumer */ for (i = 0; i < nthreads; i++) { Pthread_join(tid_produce[i], NULL); printf("count[%d] = %d\n", i, count[i]); } Pthread_join(tid_consume, NULL); exit(0);}/**//* end main *//**//* include prodcons */void *produce(void *arg){ for ( ; ; ) { Pthread_mutex_lock(&put.mutex); if (put.nput >= nitems) { Pthread_mutex_unlock(&put.mutex); return(NULL); /**//* array is full, we're done */ } buff[put.nput] = put.nval; put.nput++; put.nval++; Pthread_mutex_unlock(&put.mutex); Pthread_mutex_lock(&nready.mutex); if (nready.nready == 0) Pthread_cond_signal(&nready.cond);//发出信号唤醒消费者 nready.nready++;//置为1 Pthread_mutex_unlock(&nready.mutex); *((int *) arg) += 1; }}void *consume(void *arg){ int i; for (i = 0; i < nitems; i++) { Pthread_mutex_lock(&nready.mutex); while (nready.nready == 0) Pthread_cond_wait(&nready.cond, &nready.mutex);//wait条件变量 nready.nready--;//置为0 Pthread_mutex_unlock(&nready.mutex); if (buff[i] != i) printf("buff[%d] = %d\n", i, buff[i]); } return(NULL);}/**//* end prodcons */
