线程相关函数(4)-pthread_mutex_lock(), pthread_mutex_unlock() 互斥锁

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

#define NLOOP 5000

static pthread_mutex_t counter_mutex = PTHREAD_MUTEX_INITIALIZER;
static int counter;

void *doit(void *);


int main()
{
    pthread_t tidA, tidB;
    pthread_create(&tidA, NULL, doit, NULL);
    pthread_create(&tidB, NULL, doit, NULL);

    /*wait for both threads to terminate*/
    pthread_join(tidA, NULL);
    pthread_join(tidB, NULL);
    
    return 0;
}


void *doit(void *arg)
{    
    int i, val;
    for (i=0; i<NLOOP; i++) {
        pthread_mutex_lock(&counter_mutex);
        val = counter;
        printf("%x: %d\n", (unsigned int)pthread_self(), val+1);
        counter = val + 1;
        pthread_mutex_unlock(&counter_mutex);
    }
    return NULL;
}