使用简单的 CRITICAL_SECTION，似乎陷入僵局

发布于 2025-01-07 14:41:34 字数 982 浏览 0 评论 0原文

我有一个使用 CRITICAL_SECTION 的简单 C 程序。由于某种原因它似乎一次又一次地进入CRITICAL_SECTION并且没有真正执行里面的代码，导致线程死锁。我似乎找不到原因。

这是代码：

#include <windows.h>
#include <iostream>

#define N 100000000

CRITICAL_SECTION cs;

static DWORD WINAPI safe_increment(void *param)
{
   volatile long* x = (volatile long*)param;
   for(int i=0;i<N;++i)
      EnterCriticalSection(&cs);
      ++(*x);
      LeaveCriticalSection(&cs);
   return 0;
}

void main()
{
   InitializeCriticalSection(&cs);

  volatile long x = 0;

  HANDLE h[2];
  DWORD thread_id;

   int x = 0;

   h[0] = CreateThread(NULL,0,safe_increment,(void*)&x,0,&thread_id);
   h[1] = CreateThread(NULL,0,safe_increment,(void*)&x,0,&thread_id);
   WaitForMultipleObjects(2,h,TRUE,INFINITE);
   CloseHandle(h[0]);
   CloseHandle(h[1]);

   DeleteCriticalSection(&cs);

   std::cout << "Result of safe increment: " << x << "\n";
}

谢谢！

罗伊.

原文

i have a simple C program that uses CRITICAL_SECTION.
for some reason it seem to enter the CRITICAL_SECTION again and again and not really execute the code inside, causing the threads to deadlocked.
i cannot seem to find the reason for this.

here is the code:

#include <windows.h>
#include <iostream>

#define N 100000000

CRITICAL_SECTION cs;

static DWORD WINAPI safe_increment(void *param)
{
   volatile long* x = (volatile long*)param;
   for(int i=0;i<N;++i)
      EnterCriticalSection(&cs);
      ++(*x);
      LeaveCriticalSection(&cs);
   return 0;
}

void main()
{
   InitializeCriticalSection(&cs);

  volatile long x = 0;

  HANDLE h[2];
  DWORD thread_id;

   int x = 0;

   h[0] = CreateThread(NULL,0,safe_increment,(void*)&x,0,&thread_id);
   h[1] = CreateThread(NULL,0,safe_increment,(void*)&x,0,&thread_id);
   WaitForMultipleObjects(2,h,TRUE,INFINITE);
   CloseHandle(h[0]);
   CloseHandle(h[1]);

   DeleteCriticalSection(&cs);

   std::cout << "Result of safe increment: " << x << "\n";
}

thank you!

Roy.

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じее 2025-01-14 14:41:34

for 循环中出现错误。应该是：

for(int i=0;i<N;++i)
{ // <---
      EnterCriticalSection(&cs);
      ++(*x);
      LeaveCriticalSection(&cs);
} // <---

没有大括号，因此 for 循环仅执行 EnterCriticalSection() 而没有执行其他任何操作。获取临界区的第一个线程从未释放它：死锁。

Mistake in for loop. Should be:

for(int i=0;i<N;++i)
{ // <---
      EnterCriticalSection(&cs);
      ++(*x);
      LeaveCriticalSection(&cs);
} // <---

No braces so the for loop only executed EnterCriticalSection() and nothing else. The first thread that acquired the critical section never released it: deadlock.

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