/* Copyright (c) 2020, Dive into Systems, LLC
 * https://diveintosystems.org/
 * /

/*
 * pthreads program with a race condition (used in the gdb pthreads example)
 * to compile:
 *   gcc -g racecond.c -pthread
 */

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

// the thread main routine must match this prototype:
void *worker_loop(void *arg);

// global variables shared by all threads
static unsigned long long count;

/***************************************************************/
int main(int argc, char **argv) {

    pthread_t *tids;
    int ret, i, ntids, *tid_args;

    if (argc != 2) {
        printf("usage: ./racecond num_threads\n");
        exit(1);
    }
    ntids = atoi(argv[1]);
    // ensure a valid number for ntids
    if ((ntids < 1) || (ntids > 100)) { ntids = 10; }

    tids = (pthread_t *)malloc(sizeof(pthread_t)*ntids);
    if (!tids) {
        perror("malloc pthread_t array");
        exit(1);
    }
    if (!(tid_args = (int *)malloc(sizeof(int)*ntids))) {
        perror("malloc tid_args array");
        exit(1);
    }

    count = 0;
    for (i = 0; i < ntids; i++) {
        tid_args[i] = i;
        ret = pthread_create(&tids[i], 0, worker_loop, &tid_args[i]);
        if (ret) {
            perror("Error pthread_create\n");
            exit(1);
        }
    }

    for (i = 0; i < ntids; i++) {
        pthread_join(tids[i], 0);
    }
    printf("count = %llu\n", count);

    free ((int *)tid_args);
    free ((pthread_t *)tids);
    exit(0);
}
/****************************************************************/
// thread main loop
//   arg: an int value specifying a logical tid value
void *worker_loop(void *arg) {

    int myid, i;
    myid = *((int *)arg);

    printf("hello I'm thread %d with pthread_id %lu\n",
            myid, pthread_self());

    for (i = 0; i < 10000; i++) {
        count += i;
    }

    return (void *)0;
}