[xyos]信号量实现PV操作

[harryxiyou]

以下是以信号量的形式实现的PV操作，如有不足之处，请指正。

/*

 *  src/process_control/producer_consumer.c

 *

 *

 *  Harry Wei <harry...@gmail.com> (C) 2011

 */

#include <glib.h>

#include <stdlib.h>

#include <stdio.h>

#include <stdint.h>

#include <sys/types.h>

#include <sys/ipc.h>

#include <sys/shm.h>

#include <unistd.h>

#include <sys/sem.h>

#include "semun.h"

#undef P

#undef V

/*

 * The following program is just for demonstrating 

 * producer-consumer model with pv-operation concurrently.

 * This has been included by my libxyos, you can use it

 * by linking this library and include the relevant header

 * file. These codes are all under the GPL v3 or later 

 * version so feel free to change it for yourself.

 */

#if 0

#ifdef _SEMUN_H

#define _SEMNU_H

union semnu {

int val;

struct semid_ds *buf;

unsigned short *array;

struct seminfo *__buf;

};

#endif

#endif

/*

 * p: the p operation for applying resource.

 * @para semid: the semaphore's id.

 * @para index: the semaphore's index.

 * @return: if error happens return -1, return 0 is right.

 */

static int p(int semid, int index)

{

#if 1

struct sembuf buf = {

.sem_num = 0, /*semaphore number*/

.sem_op = -1, /*semaphore operation*/

.sem_flg = SEM_UNDO /*operation flags*/

};

#endif

if (0 > index) {

g_message("%s -- index of the semaphore is invalid!\n", __func__);

return -1;

}

buf.sem_num = index;

if (-1 == semop(semid, &buf, 1)) {

g_message("%s -- process %d p operation failed!\n", __func__, getpid());

return -1;

}

return 0;

}

/*

 * v: the v operation for releasing resource.

 * @para semid: the semaphore's id.

 * @para index: the semaphore's index.

 * @return: if error happens return -1, return 0 is right.

 */

static int v(int semid, int index)

{

#if 1

struct sembuf buf = {

.sem_num = 0,

/* release resource, add the buf.sem_op to semval */

.sem_op = 1,

.sem_flg = SEM_UNDO

};

#endif

if (0 > index) {

g_message("%s -- index of the semaphore is invalid!\n", __func__);

return -1;

}

buf.sem_num = index;

if (-1 == semop(semid, &buf, 1)) {

g_message("%s -- process %d v operation failed!\n", __func__, getpid());

return -1;

}

return 0;

}

/*

 * producer_consumer_pv: use the pv operations for access cs.

 * @para pid_num: the amount of accessing process.

 * @return: if error happens return -1, return 0 is right.

 */

int producer_consumer_pv(uint32_t pid_num)

{

pid_t pid;

key_t key;

uint32_t i = 0;

uint32_t j = 0;

uint32_t proj_id = 2;

uint32_t semid = 0;

union semun arg;

// memset(&arg, 0, sizeof(union semun));

/* convert a pathname and a project identifier to a system v ipc key */

if (-1 == (key = ftok(".", proj_id))) {

g_message("%s -- generating IPC key failed!\n", __func__);

return -1;

}

/* get a semaphore set identifier */

if (-1 == (semid = semget(key, 1, IPC_CREAT | 0666))) {

g_message("%s -- creating semaphore set failed!\n", __func__);

return -1;

}

arg.val = 1;

/* semaphore control operations */

if (-1 == semctl(semid, 0, SETVAL, arg)) {

g_message("%s -- set semval failed!\n", __func__);

return -1;

}

for (i = 0; i < pid_num; i++) {

pid = fork();

if (0 > pid) {

g_message("%s -- fork error!\n", __func__);

return -1;

} else if (0 == pid) {

if (-1 == (semid = semget(key, 1, 0))) {

exit(EXIT_FAILURE);

}

#if defined(P)

if (-1 == p(semid, 0)) {

exit(EXIT_FAILURE);

}

#endif

g_print("%s -- process %d enter the critical section!!!\n", __func__, getpid());

sleep(1);

g_print("%s -- process %d access the critical section!!!\n", __func__, getpid());

sleep(1);

g_print("%s -- process %d leave the critical section!!!\n", __func__, getpid());

sleep(1);

#if defined(V)

if (-1 == v(semid, 0)) {

exit(EXIT_FAILURE);

}

#endif

return 0;

}

}

for (i = 0; i < pid_num; i++) {

wait(NULL);

}

if (-1 == semctl(semid, 0, IPC_RMID, 0)) {

g_message("%s -- destroy the sem set failed!\n", __func__);

return -1;

}

return 0;

}

--
Thanks.
Best Regards.
Harry Wei.
Do what u like!