尽管互斥锁，线程中的种族条件

Question

此代码计算数组中所有整数的总和，将工作平均分配到多个线程之间。但是，每隔一段时间，线程号以及线程的localsum就会混乱。我假设这是因为void * param和globalindex被多个线程同时访问。即使我在此代码中互锁了每个全局变量，也没有发生这样的事实。我该如何解决？

pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

using namespace std;
int y =0;
int sum=0;
int array[1000000];
int x=0;
int leftoverHandle = 0;
int globalindex = 0;
int eachThreadHandles =0;

void* add(void* param){
    pthread_mutex_lock(&mutex);
    int localindexup = globalindex + eachThreadHandles;
    int localindexdown = globalindex;
    int localsum=0;
    long localparam = (long)param;

    if(y != leftoverHandle ){
            localindexup++;
            y++;

    }
    pthread_mutex_unlock(&mutex);


    while(localindexdown<localindexup){

            pthread_mutex_lock(&mutex);
            sum = sum+array[localindexdown];
            localsum = localsum+array[localindexdown];
            localindexdown++;
            pthread_mutex_unlock(&mutex);


    }




    pthread_mutex_lock(&mutex);
    globalindex = localindexdown;
    printf("Thread %ld", localparam);
    printf(": %d\n", localsum);
    pthread_mutex_unlock(&mutex);
}

Answer 1

作为我的评论的后续内容，将条件置于互斥区域内将解决问题：

while(1)
{
            pthread_mutex_lock(&mutex);
            if(localindexdown<localindexup)
               break; 
            sum = sum+array[localindexdown];
            localsum = localsum+array[localindexdown];
            localindexdown++;
            pthread_mutex_unlock(&mutex);
}