Question

我这里有一个程序：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <sys/msg.h>
#include <sys/wait.h>
#include <errno.h>

#include "linkedlist.h"
#include "globals.h"
#include "card.h"
#include "logging.h"
#include "stack.h"
#include "servers.h"
#include "player.h"

#define VERSION "0.1"

#define ERR -1

/*
 * Main function runs, loads 5 named table objects. For each table
 * created a fork is created for that specific table object that
 * allows each table to run independently.
 *
 * Usernames details are also created and prepared. These are hardcoded
 * until I add database logic later.
 *
 * After the tables are prepared, the main function starts a server
 * listening thread that waits for UNIX sockets to connect to it. When
 * they arrive it spawns a handling thread that does a quick login check
 * and then asks the user which of the named tables they want to play on
 *
 * The socket information is then connected to the table, so the table can
 * then communicate with user. When the table is full, the table algorithm
 * is responcible for basically looping contineously, creating new "games"
 * until only one player is left. He is the winner. When he wins, the table
 * exits.
 *
 * the game loop does all the real work for the texas holdem game, hosting
 * rounds of bets, dealing cards etc.
 */

void table_process(int tables_id);
void main_game_loop(void);

int main(int argc, char **argv)
{
  int main_process_id;
  int connection_process_id;

  char table_config_name[8];
  char *table_name;
  stack *my_deck;
  card *current_card;
  int i;
  int s;

  printf("------------ PRT POKER -----------\nA texas holdem poker server\n~~~~Version: %s~~~~~~~\n", VERSION);

  config_load("poker.conf");
  logging_init();

  if (key = ftok("/mnt/mydocuments/git/texas_holdem/poker", 'a') == -1)
  {
    logging_critical("Call to ftok failed");
    exit(1);
  }

//  if ((msg_queue = msgget(key, 0644 | IPC_CREAT)) == -1)
//  {
//    logging_critical("call to msgget failed");
//    exit(1);
//  }

  //read int the list of tables from the configuration file

  config_get_int("players_per_table", &player_count);
  logging_info("players per table: %i", *player_count);

  config_get_int("table_count", &table_count);
  logging_info("number of tables: %i", *table_count);

  table_names = malloc(sizeof(char*) * (*table_count));

  logging_info("Table count: %d", *table_count);

  for (i = 0; i < *table_count; i++)
  {
    sprintf(table_config_name, "table_%d", (i + 1));  
    config_get_string(table_config_name, &table_name);

    table_names[i] = table_name;

    logging_info("Created table %d: %s", i, table_name);

    if (fork() == 0)
    {
      table_process(i);
      _exit(0);
    }
  }

  main_process_id = getpid();

  connection_process_id = fork();
  logging_info("connecton process: %d", connection_process_id);

  if (connection_process_id == 0)
  {
    wait_for_players();
    _exit(0);
  }
  else
    waitpid(connection_process_id, &s, 0);

  logging_info("Application ended");
  return 0;
}

void table_process(int table_id)
{
  linkedlist *players;
  player *p;
  int players_added;

  if ((msg_queue = msgget(key, 0644 | IPC_CREAT)) == -1)
  {
    logging_critical("call to msgget failed");
    exit(1);
  }

  logging_info("table %s (%i) running in process %d", table_names[table_id], table_id, getpid());

  players = linkedlist_new();

  players_added = *player_count;
  while (players_added > 0)
  {
    logging_info("still waiting for %i players to join %s with queue id %i", players_added, table_names[table_id], table_id + MSG_QUEUE_OFFSET);


    //THIS DOESN'T WORK!!!! IT DOESN'T WAKE UP
    if (msgrcv(msg_queue, &p, sizeof(player), table_id + MSG_QUEUE_OFFSET, 0) == -1)
    {
      logging_critical("recieving from message queue failed");
      _exit(1);
    }
    else
      logging_info("played joined %s", table_names[table_id]);

    logging_debug("player = %s, %s", p->name, p->password);

    players_added--;
  }

  logging_info("table %s ready to start!!!!!", table_names[table_id]);
}

void main_game_loop(void)
{
  logging_debug("main_game_loop");
}

程序应该启动并分成4个线程。前三个线程调用msgget（）来创建系统V消息队列。

然后他们都调用msgrcv（）并等待不同的id发生。

第四个线程侦听连接客户端，然后调用msgsnd（）。出于某种原因，没有一个等待消息的分叉再次醒来。

我确定消息队列是正确的。
我在msgsrcv之前有一个print语句，所以我可以看到fork发生了正确的每个语句。之后还有一个打印声明，所以我可以看到代码没有通过它。
我从命令提示符运行了ipcs。
肯定会创建一个消息队列，并且其中有一条消息。
如果我将msgrcv更改为“0”，那么其中一个线程将被唤醒，但这不是我想要的行为。
msgget（）不会抛出错误。
msgsnd（）没有抛出错误。
我很肯定结构中的id是正确的。

任何想法我做错了什么？

Answer 1

至少有一件事是错的：你已经将“p”声明为指向玩家的指针，并且在将其传递给msgrcv时再次获取其地址。更重要的是，你传递的指针大小可能太大（即sizeof（播放器）＆gt; sizeof（播放器*））。堆栈腐败等待发生。

然后，尝试使用strace（在Linux上;在Solaris上使用truss）来实时查看正在发生的事情。

为什么我不能使用fork（）使用系统V消息队列？

1 个答案: