MultiThreading read and write for Hazard Pointer Logic in C

multithread_test_zone.c

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

#define THREAD_RUN 100
typedef struct $
{
    char s[50];
} concurrent_update;

static concurrent_update *a;

static concurrent_update *cus;
void * write(void* thr_data) {
    int n;
    concurrent_update *cu = cus + (*(int*)thr_data);

// RETRY:
    for (n = 0; n < 1000; ++n) {
        sprintf(cu->s, "thread id %ld\n", pthread_self() );
        a = cu;
    }
    // goto RETRY;

    // free(cu);
    return 0;
}

void * read(void* thr_data)
{
    int n;
// RETRY:
    for (n = 0; n < 1000; ++n) {
        printf("%s\n ", a->s);
    }
    // goto RETRY;
    return 0;
}



int main(void)
{
    int n;
    pthread_t read_thr[THREAD_RUN];
    pthread_t write_thr[THREAD_RUN];
    concurrent_update *start = malloc(sizeof(concurrent_update));
    cus = malloc(THREAD_RUN * sizeof(concurrent_update));
    strcpy(start->s, "abcdeti");
    a = start;
    for (n = 0; n < THREAD_RUN; ++n) {
        pthread_create(&write_thr[n], NULL, write, &n);
        pthread_create(&read_thr[n], NULL, read, &n);
    }



    for (n = 0; n < THREAD_RUN; ++n)
        pthread_join(read_thr[n], NULL);

    for (n = 0; n < THREAD_RUN; ++n)
        pthread_join(write_thr[n], NULL);

    free(start);

    free(cus);

}