Unix IPC之Posix信号量实现生产者消费者
采用多生产者，多消费者模型。
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/** * 生产者 */P(nempty);P(mutex);// 写入一个空闲位置V(mutex);V(nstored);/** * 消费者 */P(nstored);P(mutex):// 清空一个非空闲位置V(mutex);V(nempty); |
全局性说明：
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#include "unpipc.h"#define NBUFF 10#define MAXNTHREADS 100int nitems, nproducers, nconsumers; /* read-only */struct /* data shared by producers and consumers */{ int buff[NBUFF]; int nput; /* item number: 0, 1, 2, ... */ int nputval; /* value to store in buff[] */ int nget; /* item number: 0, 1, 2, ... */ int ngetval; /* value fetched from buff[] */ sem_t mutex, nempty, nstored; /* semaphores, not pointers */} shared;void *produce(void *);void *consume(void *);/* end globals */ |
主函数：
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/* include main */intmain(int argc, char **argv){ int i, prodcount[MAXNTHREADS], conscount[MAXNTHREADS]; pthread_t tid_produce[MAXNTHREADS], tid_consume[MAXNTHREADS]; if (argc != 4) err_quit("usage: prodcons4 <#items> <#producers> <#consumers>"); nitems = atoi(argv[1]); nproducers = min(atoi(argv[2]), MAXNTHREADS); nconsumers = min(atoi(argv[3]), MAXNTHREADS); /* 4initialize three semaphores */ Sem_init(&shared.mutex, 0, 1); Sem_init(&shared.nempty, 0, NBUFF); Sem_init(&shared.nstored, 0, 0); /* 4create all producers and all consumers */ Set_concurrency(nproducers + nconsumers); for (i = 0; i < nproducers; i++) { prodcount[i] = 0; Pthread_create(&tid_produce[i], NULL, produce, &prodcount[i]); } for (i = 0; i < nconsumers; i++) { conscount[i] = 0; Pthread_create(&tid_consume[i], NULL, consume, &conscount[i]); } /* 4wait for all producers and all consumers */ for (i = 0; i < nproducers; i++) { Pthread_join(tid_produce[i], NULL); printf("producer count[%d] = %d\n", i, prodcount[i]); } for (i = 0; i < nconsumers; i++) { Pthread_join(tid_consume[i], NULL); printf("consumer count[%d] = %d\n", i, conscount[i]); } Sem_destroy(&shared.mutex); Sem_destroy(&shared.nempty); Sem_destroy(&shared.nstored); exit(0);}/* end main */ |
生产者线程：
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/* include produce */void *produce(void *arg){ for ( ; ; ) { Sem_wait(&shared.nempty); /* wait for at least 1 empty slot */ Sem_wait(&shared.mutex); if (shared.nput >= nitems) { Sem_post(&shared.nstored); /* let consumers terminate */ Sem_post(&shared.nempty); Sem_post(&shared.mutex); return(NULL); /* all done */ } shared.buff[shared.nput % NBUFF] = shared.nputval; shared.nput++; shared.nputval++; Sem_post(&shared.mutex); Sem_post(&shared.nstored); /* 1 more stored item */ *((int *) arg) += 1; }}/* end produce */ |
消费者线程：
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/* include consume */void *consume(void *arg){ int i; for ( ; ; ) { Sem_wait(&shared.nstored); /* wait for at least 1 stored item */ Sem_wait(&shared.mutex); if (shared.nget >= nitems) { Sem_post(&shared.nstored); Sem_post(&shared.mutex); return(NULL); /* all done */ } i = shared.nget % NBUFF; if (shared.buff[i] != shared.ngetval) printf("error: buff[%d] = %d\n", i, shared.buff[i]); shared.nget++; shared.ngetval++; Sem_post(&shared.mutex); Sem_post(&shared.nempty); /* 1 more empty slot */ *((int *) arg) += 1; }}/* end consume */ |
