SMP Demo Code: Execute a bunch of threads, showing by screen which cpu are executing each - 32-bit version

smp_demo_pthread.c

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/types.h>

#define MS_STOP_TIME 100 
#define NUM_THREADS 16

unsigned int get_apic_id(void){
    unsigned int cpu_eax, cpu_ebx, cpu_ecx, cpu_edx;
      cpu_eax = 0x1;
      asm (
        "mov %%eax, %0\n\t"
        "cpuid\n\t"
        "mov %0, %%eax\n\t"
        "mov %1, %%ebx\n\t"
        "mov %2, %%ecx\n\t"
        "mov %3, %%edx\n\t"
        : "=r" (cpu_eax), "=r" (cpu_ebx), "=r" (cpu_ecx), "=r" (cpu_edx)
        : "0" (cpu_eax)
      );
      
      unsigned int apic_id = cpu_ebx >> 24; 
     
      return apic_id;
}

void *thread_routine()
{  
   while(1){      
      unsigned int apic_id = get_apic_id();
      printf ("Thread %u - %x\n",pthread_self(), apic_id);
      
      volatile int time = 0, time2;
      while(time < MS_STOP_TIME*100000){
        time++;
        time2 = time+1;
      }
    }
}

int main()
{
    pthread_t threads[NUM_THREADS];
    
    for(int i = 0; i < NUM_THREADS; i++){
      pthread_create(&threads[i],NULL,(void *) &thread_routine, NULL);
    }
    
    for(int i = 0; i < NUM_THREADS; i++){
      pthread_join(threads[i],NULL);
    }
}