c - 多线程 C 应用程序中的访问冲突

Question

我正在尝试编写一个简单的多线程 C 应用程序。我希望主线程暂停，直到工作线程设置了某个标志。因此，对于我的线程函数参数，我传递了一个包含标志的结构。当我在工作线程中分配标志时，我遇到了访问冲突。我正在使用 Mutex 从理论上防止同时访问在主应用程序和工作线程之间共享的这个结构实例。有人能指出我正确的方向吗？完整的项目代码如下。我在 THREADFUNCS.C 文件的注释中指出了错误行。

全局.H

#ifndef _globals_h
#define _globals_h

#include <windows.h>


static HANDLE ghMutex;


#endif

线程通信.H

#ifndef _threadcom_h
#define _threadcom_h

typedef struct { 
   char bContinueMain;
} RComData;

#endif

线程函数.H

#ifndef _threadfuncs_h
#define _threadfuncs_h 

#include <windows.h>

extern DWORD WINAPI ThreadA(LPVOID params);

#endif

线程函数.C

#include <stdio.h>
#include "threadcom.h"
#include "threadfuncs.h"
#include "globals.h"

DWORD WINAPI ThreadA(LPVOID params)
{
   RComData* pr = (RComData*)params;
   int i;

   printf("You are in thread A.\n");
   WaitForSingleObject(ghMutex, INFINITE);
   pr->bContinueMain = TRUE; /* ACCESS VIOLATION HERE */
   ReleaseMutex(ghMutex);
   for (i=0; i<10; ++i)
   {
      printf("Printing THREAD A line %i.\n", i);
   }
}

主程序

#include <windows.h>
#include <stdio.h>
#include "threadfuncs.h"
#include "threadcom.h"
#include "globals.h"

void WaitForGoAhead(RComData* pr)
{
   char bGo = FALSE;
   while (!bGo)
   {
      WaitForSingleObject(ghMutex, INFINITE);
      if (pr->bContinueMain)
         bGo = TRUE;
      ReleaseMutex(ghMutex);
   }
}

int main(void)
{
   int i;
   HANDLE hThreadId = -1;
   RComData r = { FALSE };

   hThreadId = CreateThread(0, 0, ThreadA, 0, &r, &hThreadId);
   WaitForSingleObject(hThreadId, 1);
   if (hThreadId > 0)
   {
      printf("Thread has been launched.\n");
      ghMutex = CreateMutex(0, FALSE, 0);
      WaitForGoAhead(&r);
      for (i=0; i<10; ++i)
      {
         printf("Printing main proc line %i.\n", i);
      }
      WaitForSingleObject(hThreadId, INFINITE);
      printf("Thread is complete.\n");
      CloseHandle(ghMutex);
      CloseHandle(hThreadId);
   }
   else
   {
      printf("Thread failed to created.\n");
   }

   printf("Press any key to exit...");
   getchar();
   return 0;
}

谢谢。

Answer 1

您需要在创建线程之前创建互斥量。

现在您的线程将在无效句柄上 WaitForSingleObject