Lamport's bakery in C

bakery.c

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <inttypes.h>
#include <errno.h>

#define NUM_THREADS 3
#define NUM_SECTIONS 1

volatile int i = 0;

uint8_t joining[NUM_SECTIONS][NUM_THREADS]={0!=0};
uint64_t numbers[NUM_SECTIONS][NUM_THREADS]={0};


uint64_t max(long sid) {
  uint64_t result = 0;
  for (int idx = 0; idx < NUM_THREADS; idx++) 
    if (numbers[sid][idx]>result) result = numbers[sid][idx];
  return result;
}

void lock(long sid, long pid) {
  joining[sid][pid] = (0==0);
  numbers[sid][pid] = 1 + max(sid);
  joining[sid][pid] = (0!=0);
  for (int idx=0; idx < NUM_THREADS; idx++) {
    while (joining[sid][idx]) {}
    while ((numbers[sid][idx] != 0) && 
           (numbers[sid][idx]<numbers[sid][pid] || 
            (numbers[sid][idx]==numbers[sid][pid] && idx<pid))) {}
  }
}

void unlock(long sid, long pid) {
  numbers[sid][pid] = 0;
}

void *thr(void *threadid) {
  long tid = (long)threadid;
  printf("[%ld]\n", tid);
  lock(0, tid);
  #ifdef DEBUG
    printf("Joining: "); for (int idx=0; idx < NUM_THREADS; idx++) printf("%d,", joining[0][idx]); printf("\n");
    printf("Numbers: "); for (int idx=0; idx < NUM_THREADS; idx++) printf("%ld,", numbers[0][idx]); printf("\n");
  #endif
  i = 0;
  for (int idx = 0; idx < 1000000000; idx++) i = i + 1;
  unlock(0, tid);
  pthread_exit(NULL);
}


void main ()  {
  pthread_t threads[NUM_THREADS];
  pthread_attr_t attr;
  void *status;
  int rc;

  pthread_attr_init(&attr);
  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

  for(long t=0; t<NUM_THREADS; t++){
    printf("[M] creating thread %ld\n", t);
    rc = pthread_create(&threads[t], &attr, thr, (void *)t);
    if (rc) {
      printf("[M] ERROR; return code from pthread_create() is %d\n", rc);
      exit(-1);
    }
  }

  for(long t=0; t<NUM_THREADS; t++) {
    rc = pthread_join(threads[t], &status);
    if (rc) {
      printf("[M] ERROR; return code from pthread_join() is %d\n", rc);
      exit(-1);
      }
    printf("[M] completed join with thread %ld having a status of %ld\n",t,(long)status);
  }

  printf("i = %d\n", i); // Should print 1000000000

  pthread_attr_destroy(&attr);
  pthread_exit(NULL);
}

Makefile

PROG = bakery

all: clean $(PROG)
$(PROG): $(PROG).c
	gcc -g -o $@ -pthread -O0 $(CFLAGS) $<
clean: 
	-rm $(PROG)