有趣的例子，干得好!
尝试更改线程优先级，看看会发生什么，从而看到不同的计数（请参阅下面的代码）。
也许可以考虑添加一个信号量，在两个线程之间乒乓计数，这样它们就可以平等地执行，并报告3999999和4000000作为最终计数。
我相信你也有其他的想法，谢谢你的帖子。

gcc main.c -o main
./main
Initial Counter Value: 0
I am thread 2. I counted 2000000 times. Global counter = 3880728
I am thread 1. I counted 2000000 times. Global counter = 4000000
Final Counter: 4000000

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>

#define MAX 2000000UL
pthread_mutex_t lock;
//pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

struct shared_data
{
    int value;     /* shared variable to store result*/
    
};

struct shared_data  *counter;

void* thread1Func(void * tid){
    uint32_t i = 0;
    while(i < MAX){
        
        if(pthread_mutex_trylock(&lock) == 0){
            counter->value++;
            pthread_mutex_unlock(&lock);
            i++;
        }
    }
    printf("I am thread 1. I counted %d times. Global counter = %d\n", i, counter->value);
    return NULL;
}

void* thread2Func(void * tid){
    
    uint32_t i = 0;
    while(i < MAX){
        
        if(pthread_mutex_trylock(&lock) == 0){
            counter->value++;
            pthread_mutex_unlock(&lock);
            i++;
        }

    }
    printf("I am thread 2. I counted %d times. Global counter = %d\n", i, counter->value);
    return NULL;
}

int main() {
    
    counter = (struct shared_data *) malloc(sizeof(struct shared_data));
    printf("Initial Counter Value: %d\n", counter->value);
    
    pthread_t thread1;
    pthread_t thread2;
    pthread_mutex_init(&lock, NULL);

    pthread_attr_t attr;
    struct sched_param sch_params;
    pthread_attr_init(&attr);
    pthread_attr_getschedparam(&attr, &sch_params);
    sch_params.sched_priority = 99;
    //pthread_attr_setschedpolicy(&attr, SCHED_RR);
    pthread_attr_setschedparam(&attr, &sch_params);
    pthread_create(&thread1, &attr, thread1Func, NULL);

    sch_params.sched_priority = 1;
    pthread_create(&thread2, &attr, thread2Func, NULL);
    
    
    pthread_join(thread1,NULL);
    pthread_join(thread2,NULL);
    
    
    printf("Final Counter: %d\n", counter->value);
    return 0;
}