Use pthread_cancel, pthread_setcancelstate, pthread_setcanceltype to Cancel a thread.

sample_thread_cancel.c

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

void *thread_func(void *arg);

int main(void) {
    int rs;
    pthread_t thd;
    void *thread_result;

    rs = pthread_create(&thd, NULL, thread_func, NULL);
    if (rs != 0) {
        perror("Thread creation failed!\n");
        exit(EXIT_FAILURE);
    }

    sleep(3);

    rs = pthread_cancel(thd);
    if (rs != 0) {
        perror("Thread cancelation failed\n");
        exit(EXIT_FAILURE);
    }
    
    rs = pthread_join(thd, &thread_result);
    if (rs != 0) {
        perror("Thread Join failed\n");
        exit(EXIT_FAILURE);
    }
    exit(EXIT_FAILURE);
}

void *thread_func(void *arg) {
    int i, rs;
    rs = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
    if (rs != 0) {
        perror("Thread pthread_setcancelstate failed\n");
        exit(EXIT_FAILURE);
    }

    // PTHREAD_CANCEL_DEFERRED means that it will wait the pthread_join, 
    // pthread_cond_wait, pthread_cond_timewait.. to be call when the 
    // thread receive cancel message.
    rs = pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);
    if (rs != 0) {
        perror("Thread pthread_setcanceltype failed\n");
        exit(EXIT_FAILURE);
    }

    printf("thread_func is running\n");
    for (i = 0; i < 10; i++) {
        perror("Thread is stil running (%d) ... \n", i);
        sleep(1);
    }

    pthread_exit(0);
}