process_shared_mutex.c

来自「linux下多线程程序设计,包括signals,mutex,simple_onc」· C语言 代码 · 共 82 行

/********************************************************
 * An example source module to accompany...
 *
 * "Using POSIX Threads: Programming with Pthreads"
 *     by Brad nichols, Dick Buttlar, Jackie Farrell
 *     O'Reilly & Associates, Inc.
 *
 ********************************************************
 * process_shared_mutex.c -- 
 *
 * Demonstrating the shared process mutex
 */

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/wait.h>


#include <pthread.h>



int   shared_mem_id;
int   *shared_mem_ptr;

pthread_mutexattr_t mutex_shared_attr;
pthread_mutex_t	*mptr;

extern int	main(void)
{
	pid_t  child_pid;
	int  status, rtn;
	
	/* initialize shared memory segment */
	if ((shared_mem_id = shmget(IPC_PRIVATE, 1*sizeof(pthread_mutex_t), 0660)) < 0)
		perror("shmget"), exit(1) ;
	
	if ((shared_mem_ptr = (int *)shmat(shared_mem_id, (void *)0, 0)) == NULL)
		perror("shmat"), exit(1);
	
	mptr = (pthread_mutex_t *)shared_mem_ptr;
	
	
	if (( rtn = pthread_mutexattr_init(&mutex_shared_attr)) != 0) 
		fprintf(stderr,"pthreas_mutexattr_init: %s",strerror(rtn)),exit(1);
	
	if (( rtn = pthread_mutexattr_setpshared(&mutex_shared_attr,PTHREAD_PROCESS_SHARED)) != 0)
		fprintf(stderr,"pthread_mutexattr_setpshared %s",strerror(rtn)),exit(1);
	
	if (( rtn = pthread_mutex_init(mptr, &mutex_shared_attr)) != 0)
		fprintf(stderr,"pthread_mutex_init %s",strerror(rtn)), exit(1);
	
	
	if ((child_pid = fork()) == 0) 
	{
		/* child */
		if ((rtn = pthread_mutex_lock(mptr)) != 0)
			fprintf(stderr,"child:pthread_mutex_lock %s",strerror(rtn)),exit(1);
		sleep(1);
		if ((rtn = pthread_mutex_unlock(mptr)) != 0)
			fprintf(stderr,"child:pthread_unmutex_lock %s",strerror(rtn)),exit(1);
		exit(0);
	} 
	else 
	{
		/* parent */ 
		sleep(1); 
		if ((rtn = pthread_mutex_lock(mptr)) != 0)
			fprintf(stderr,"parent:pthread_mutex_lock %d",strerror(rtn)),exit(1);
		if ((rtn = pthread_mutex_unlock(mptr)) != 0)
			fprintf(stderr,"child:pthread_unmutex_lock %d",strerror(rtn)),exit(1);
		wait(&status);
	}
	
	return 0;
}