【发布时间】：2015-01-03 23:42:38
【问题描述】：
我正在尝试用信号量和分叉和共享内存做一个程序
父假设创建共享内存并将数字插入缓冲区打印完成 然后孩子将从共享内存中读取并打印数字的总和 程序运行，但只有父打印完成，而孩子没有做任何事情，
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <stdio.h>
#include <netinet/in.h>
#include <netdb.h>
#include<netinet/in.h>
#include<netdb.h>
#include<sys/wait.h>
#include<unistd.h>
#include <sys/shm.h>
char buffer[10];
char *data;
int commNo =0;
key_t key;
int shmid;
char *shrmem;
int mode;
void error(char *msg)
{
perror(msg);
exit(0);
}
int rem[10];
key_t key; /* key to pass to semget() */
key_t key1; /* key to pass to semget() */
key_t key2; /* key to pass to semget() */
key_t key3; /* key to pass to semget() */
int semflg; /* semflg to pass tosemget() */
int nsems; /* nsems to pass to semget() */
int semid; /* return value from semget() */
#define MAX_COUNT 200
#define N 100 /* shared buffer of size 100 */
void ChildProcess(void); /* child process prototype */
void ParentProcess(void); /* parent process prototype */
//things for ftok
char *path = "/tmp";
int id = 'S';
//create sembuf
//struct sembuf{
// ushort sem_num; /* semaphore index in array */
// short sem_op; /* semaphore operation */
// short sem_flg; /* operation flags */
//};
int locksem = 1; /* binary semaphore for locking-unlocking: initiall unlocked : 1 */
int emptysem = 100; /* counting semaphore for empty slots */
int fullsem = 0; /* counting semaphore for filled slots*/
struct sembuf oplock;// = (struct sembuf *) malloc(2*sizeof(struct sembuf));
//static struct sembuf oplock;
//oplock.sem_num = 0;
//oplock.sem_op = -1;
//oplock.sem_flg = SEM_UNDO;
struct sembuf opunlock; // = (struct sembuf *) malloc(2*sizeof(struct sembuf));
//static struct sembuf opunlock;
//opunlock.sem_num = 0;
//opunlock.sem_op = 1;
//opunlock.sem_flg = SEM_UNDO;
void creatmemory(){
/* make the key: */
if ((key = ftok("/tmp",1)) == -1) {
perror("ftok");
//clientnumber
exit(1);
}
/* connect to (and possibly create) the segment: */
if ((shmid = shmget(key, 15, 0644| IPC_CREAT)) == -1) {
perror("shmget");
exit(1);
}
/* attach to the segment to get a pointer to it: */
data = shmat(shmid, (void *)0, 0);
if (data == (char *)(-1)) {
perror("shmat");
exit(1);
}
}
int main(int argc, char *argv[]){
pid_t pid;
nsems = 1;
//static struct sembuf oplock;
oplock.sem_num = 0;
oplock.sem_op = -1;
oplock.sem_flg = SEM_UNDO;
//static struct sembuf opunlock;
opunlock.sem_num = 0;
opunlock.sem_op = 1;
opunlock.sem_flg = SEM_UNDO;
//to create new one
semflg = IPC_CREAT;
/* Get unique key for semaphore. */
if ((key1 = ftok(path,1)) == (key_t) -1) {
perror("IPC error: ftok"); exit(1);
}
/* Get unique key for semaphore. */
if ((key2 = ftok(path,2)) == (key_t) -1) {
perror("IPC error: ftok"); exit(1);
}
/* Get unique key for semaphore. */
if ((key3 = ftok(path,3)) == (key_t) -1) {
perror("IPC error: ftok"); exit(1);
}
pid = fork();
if (pid == 0) {
//***************************************************************************************************************
//
int n =0;
while(n < 3){
locksem = semget(key1, nsems, semflg); /* open-create locksem*/
emptysem = semget(key2, nsems, semflg);
fullsem = semget(key3, nsems, semflg);
semop(fullsem,&oplock,1); /* check filled slots */
semop(locksem,&oplock,1); /* lock shared buffer*/
// itx= remove_item();
/* remove an item from buffer */
int i;
for (i =0; i<10; i++){
rem[i] = data[i];}
bzero(buffer,10);
bzero(data,strlen(data));
/* detach from the segment: */
if (shmdt(data) == -1) {
perror("shmdt");
exit(1);
}
semop(locksem,&opunlock,1); /* unlock the buffer */
semop(emptysem,&opunlock,1); /* increment emptysem*/
//consume_item(itx);
int sum = 0;
for(i =0; i<10; i++){
sum += rem[i];}
printf("the sum is:%d \n", sum);
n++;}
}
//consumer();
else
{
creatmemory();
int n =0;
while( n < 3) {
locksem = semget(key1, nsems, semflg); /* open-create locksem*/
emptysem = semget(key2, nsems, semflg);
fullsem = semget(key3, nsems, semflg);
bzero(buffer,10);
int i;
for(i =0; i<10; i++)
buffer[i] = i;
semop(emptysem,&oplock,1); /* check empty slots */
semop(locksem,&oplock,1); /* lock shared buffer*/
/* insert item into the buffer */
strncpy(data, buffer, strlen(buffer));
printf("done \n");
semop(locksem,&opunlock,1); /* unlock the buffer */
semop(fullsem,&opunlock,1); /* increment fullsem*/
sleep(10);
n++;}
}
// producer();
}
【问题讨论】：
-
建议重新发布代码，不带制表符，在单独的行上加上右括号'}'，每行只有一个语句，等等此外，此代码甚至没有接近干净编译，有大约 20 多个错误和警告。例如，调用了函数“exit”但没有“#include
”建议编译时启用所有警告，然后修复这些警告 -
此代码无法协调共享内存部分的创建/设置/读取/销毁。如果出现问题，'error()' 函数将无法清除信号量、释放共享内存等。