Multi-threaded interview second KILL series 4---A brief analysis of interlocked series functions

Source: Internet
Author: User

In the previous article, we had a dirty reading problem, but did not give a solution to this article in this article, we mainly explain the interlocked series functions.

       Some common interlocked series functions are listed below:

       1. Increase or decrease operation

       Long__cdeclinterlockedincrement (LONG volatile* Addend);

       Long__cdeclinterlockeddecrement (LONG volatile* Addend);

       Returns the value of the variable after the increment or decrement operation is performed.

       Long__cdec InterlockedExchangeAdd (LONG volatile* Addend, Longvalue);

       Returns the value after the operation, (note) A negative number is the minus.

       2. Assignment operation

       Long__cdeclinterlockedexchange (LONG volatile* Target, Longvalue);

       Value is the new value, and the function returns the original value.

In this case, you can just use the InterlockedIncrement () function. Let's make a list of the code below.

<span style= "FONT-SIZE:14PX;" > #include <stdio.h> #include <windows.h> volatile long g_nlogincount; Number of logins unsigned int __stdcall fun (void *ppm); Thread Function const DWORD Thread_num = 50;//start thread number DWORD WINAPI threadfun (void *ppm) {Sleep];//some W          Ork should to do//g_nlogincount++;          InterlockedIncrement ((Lplong) &g_nlogincount);          Sleep (50);      return 0;          } int main () {printf ("Atomic Operation interlocked series function \ n");                    printf ("-by Morewindows (\n\n");          Repeat 20 times to observe the conflicts that result when multiple threads access the same resource int num= 20;              while (num--) {g_nlogincount = 0;              int i;              HANDLE Handle[thread_num];              for (i = 0; i < thread_num; i++) Handle[i] = CreateThread (null, 0, threadfun, NULL, 0, NULL); WaitForMultipleObjects (Thread_num, handle, TRUE, INFInite);          printf ("%d users log results after logging%d\n", Thread_num, G_nlogincount);      } return 0; } </span>

Therefore, in the multi-threaded environment, we have to think carefully about these simple statements of variable self-increment, to prevent the data access error caused by multiple threads.

Multi-threaded interview second KILL series 4---A brief analysis of interlocked series functions

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