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February 27, 2012 08:54
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PRODUCER - CONSUMER Implementation in C
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/** PRODUCER - CONSUMER PROBLEM **/ | |
#include <stdio.h> | |
#include <sys/types.h> | |
#include <sys/ipc.h> | |
#include <sys/sem.h> | |
#include <pthread.h> | |
#include <stdlib.h> | |
#define BUFSIZE 10 | |
#define MUTEX 0 | |
#define FULL 1 | |
#define EMPTY 2 | |
int semid; | |
union semun { | |
int val; /* Value for SETVAL */ | |
struct semid_ds *buf; /* Buffer for IPC_STAT, IPC_SET */ | |
unsigned short *array; /* Array for GETALL, SETALL */ | |
struct seminfo *__buf; /* Buffer for IPC_INFO (Linux-specific) */ | |
}; | |
int sem_create(int nsems) { | |
int id; | |
key_t key = 1234; | |
int semflg = IPC_CREAT | 0666; | |
id = semget(key, nsems, semflg); | |
if(id < 0) | |
{ | |
perror("semget:"); | |
exit (1); | |
} | |
return id; | |
} | |
void sem_initialise(int semno, int val) { | |
union semun un; | |
un.val = val; | |
if(semctl(semid, semno, SETVAL, un) < 0) | |
{ | |
// printf("%d\n", semno); | |
perror("semctl:"); | |
exit(2); | |
} | |
} | |
void *producer(void *id); | |
void *consumer(void *id); | |
void wait(int semno); | |
void signal(int semno); | |
int buffer[BUFSIZE], data; | |
int in = 0; | |
int out = 0; | |
int i = 10000; | |
int j = 10000; | |
int main (int argc, char *argv[]) { | |
semid = sem_create(3); | |
sem_initialise(MUTEX, 1); | |
sem_initialise(FULL, 0); | |
sem_initialise(EMPTY, 10); | |
pthread_t prod, cons; | |
pthread_create(&prod, NULL, producer, (void *)semid); | |
pthread_create(&cons, NULL, consumer, (void *)semid); | |
pthread_exit(NULL); | |
return 0; | |
} | |
void *producer(void *id) { | |
int semid = (int) id; | |
data = 0; | |
while(i--) { | |
wait(EMPTY); | |
wait(MUTEX); | |
/** Critical Section **/ | |
buffer[in] = data; | |
in = (in + 1) % BUFSIZE; | |
data = (data + 1) % BUFSIZE; | |
printf("P:%d\n", data); | |
//printf("P\n"); | |
signal(MUTEX); | |
signal(FULL); | |
} | |
pthread_exit(NULL); | |
} | |
void *consumer(void *id) { | |
int semid = (int) id; | |
while(j--) | |
{ | |
wait(FULL); | |
wait(MUTEX); | |
/** Critical Section **/ | |
data = buffer[out]; | |
out = (out + 1) % BUFSIZE; | |
printf("C:%d\n", data); | |
/** **/ | |
signal(MUTEX); | |
signal(EMPTY); | |
} | |
pthread_exit(NULL); | |
} | |
void wait(int semno) { | |
struct sembuf buf; | |
buf.sem_num = semno; | |
buf.sem_op = -1; | |
buf.sem_flg = 0; | |
if(semop(semid, &buf, 1) < 0) { | |
perror("semop:"); | |
exit(2); | |
} | |
} | |
void signal(int semno) { | |
struct sembuf buf; | |
buf.sem_num = semno; | |
buf.sem_op = 1; | |
buf.sem_flg = 0; | |
if(semop(semid, &buf, 1) < 0) | |
{ | |
perror("semop:"); | |
exit(2); | |
} | |
} |
why do we execute it as gcc foo.c -lpthread
You compile with gcc foo.c
which generates the binary a.out
(the -lpthread
is to tell gcc to link it against the pthreads lib). Then, if the compiling command works (i.e. "&&"), ./a.out
is executed, which is the generated binary.
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why do we execute it as gcc foo.c -lpthread