多个生产者，单个消费者，信号量

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91

#include <stdio.h> #include <fcntl.h> #include <stdlib.h> #include <pthread.h> #include <semaphore.h>   #define min(a,b) ((a)<(b)?(a):(b)) #define NBUFF 10 #define MAXNTHREADS 100   int nitems, nproducers; struct {     int buff[NBUFF];     int nput, nputval;     sem_t mutex, nempty, nstored; }shared;   void *produce(void *), *consume(void *);   int main(int argc, char **argv) {     int i, count[MAXNTHREADS];     pthread_t tid_produce[MAXNTHREADS], tid_consume;           if(argc!=3) {         fprintf(stderr, "./a.out <#items> <#producers>\n");         exit(-1);     }       nitems=atoi(argv[1]);     nproducers=min(atoi(argv[2]), MAXNTHREADS);           sem_init(&shared.mutex, 0, 1);     sem_init(&shared.nempty, 0, NBUFF);     sem_init(&shared.nstored, 0, 0);           pthread_setconcurrency(nproducers+1);       for(i=0;i<nproducers;i++) {         count[i]=0;         pthread_create(&tid_produce[i], NULL, produce, &count[i]);     }       pthread_create(&tid_consume, NULL, consume, NULL);       for(i=0;i<nproducers;i++) {         pthread_join(tid_produce[i], NULL);         printf("count[%d]=%d\n", i, count[i]);     }     pthread_join(tid_consume, NULL);       sem_destroy(&shared.mutex);     sem_destroy(&shared.nempty);     sem_destroy(&shared.nstored);       exit(0); }   void *produce(void *arg) {     for(;;) {         sem_wait(&shared.nempty);         sem_wait(&shared.mutex);         if(shared.nput>=nitems) {             sem_post(&shared.nempty);             sem_post(&shared.mutex);             return NULL;            }         shared.buff[shared.nput%NBUFF]=shared.nputval;         shared.nput++;         shared.nputval++;         sem_post(&shared.mutex);         sem_post(&shared.nstored);           *((int *)arg) += 1;     }     return NULL; }   void *consume(void *arg) {     int i;       for(i=0;i<nitems;i++) {         sem_wait(&shared.nstored);         sem_wait(&shared.mutex);         if(shared.buff[i%NBUFF]!=i) {             printf("buff[%d]=%d\n", i%NBUFF, shared.buff[i%NBUFF]);         }         sem_post(&shared.mutex);         sem_post(&shared.nempty);     }     return NULL; }

运行结果如下：

?

1 2 3 4 5 6 7

$ ./a.out 1000000 6 count[0]=619 count[1]=23982 count[2]=263473 count[3]=208842 count[4]=241089 count[5]=261995