在下面的代碼中,是不是將一個互斥量創建爲子對象的副本?因此,現在有兩個互斥量 - 一個在兒童中,一個在父母中。它如何同步?據我記得,你需要一個由多個進程共享的副本,以使其同步。信號量併發性
#include <semaphore.h>
#include <stdio.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/mman.h>
int main(int argc, char **argv)
{
int fd, i,count=0,nloop=10,zero=0,*ptr;
sem_t mutex;
//open a file and map it into memory
fd = open("log.txt",O_RDWR|O_CREAT,S_IRWXU);
write(fd,&zero,sizeof(int));
ptr = mmap(NULL,sizeof(int), PROT_READ|PROT_WRITE,MAP_SHARED,fd,0);
close(fd);
/* create, initialize semaphore */
if(sem_init(&mutex,1,1) < 0)
{
perror("semaphore initilization");
exit(0);
}
if (fork() == 0) { /* child process*/
for (i = 0; i < nloop; i++) {
sem_wait(&mutex);
printf("child: %d\n", (*ptr)++);
sem_post(&mutex);
}
exit(0);
}
/* back to parent process */
for (i = 0; i < nloop; i++) {
sem_wait(&mutex);
printf("parent: %d\n", (*ptr)++);
sem_post(&mutex);
}
exit(0);
}
http://stackoverflow.com/questions/8359322/how-to-share-semaphores-between-processes-using-shared-memory – 2013-03-21 20:57:36