Even_Odd_Semaphore.

Even_Odd_Semaphore.c

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <inttypes.h>
#include <semaphore.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>

/************************************
 * sem -> 0 => blocked
 * sem -> 1 => ready to accquire
 * */


#define semA_name "/semA"
#define semB_name "/semB"


#define PERROR(ret,msg)     \
    if ( ret < 0 ) {        \
        perror(msg);      \
    }

sem_t *semA, *semB;

void * Even(void *arg){
static uint32_t num = 0;

    while(1)
    {
        sem_wait(semA);
        printf("%d\n", num);
        num+=2;
        if(num >= 20)
        {
            sem_post(semB);
            printf("Exit CHILD\n");
            pthread_exit(0);
        }
        sem_post(semB);
        

    }
}

void * Odd(void *arg){
static uint32_t num = 1;

    while(1)
    {
        sem_wait(semB);
        printf("%d\n", num);
        //sleep(1);
        num+=2;
        if(num >= 20)
        {
            printf("Exit Parent\n");
            pthread_exit(0);
        }
        sem_post(semA);

    }
}

int main(int argc, char *argv[])
{
    pthread_t thd_even_id;
    pthread_t thd_odd_id;
    int ret;

    semA = sem_open(semA_name,O_CREAT, 0666,1);
    if( semA == SEM_FAILED)
    {
        perror("Failed to open semaphore");
    }

    semB = sem_open(semB_name,O_CREAT, 0666, 0);
    if( semB == SEM_FAILED)
    {
        perror("Failed to open semaphore");
    }

    ret = pthread_create(&thd_even_id,NULL,Even,NULL);
    if( ret < 0 )
    {
        perror("Error in thread creation thd_even_id");
    }
    ret = pthread_create(&thd_odd_id, NULL,Odd, NULL);
    if( ret < 0 )
    {
        perror("Error in thread creation thd_odd_id");
    }    
    ret = pthread_join(thd_even_id, NULL);
    if( ret < 0 )
    {
        perror("Error in thread joining thd_even_id");
    } 
    ret = pthread_join(thd_odd_id, NULL);
    if( ret < 0 )
    {
        perror("Error in thread joining thd_odd_id");
    } 




    //remove sempahore
    ret = sem_close(semA);
    PERROR(ret, "Failed to close semaphore A");
    ret = sem_close(semB);
    PERROR(ret, "Failed to close semaphore B");
    ret = sem_unlink(semA_name);
    PERROR(ret, "unlink failed sem A");
    ret = sem_unlink(semB_name);
    PERROR(ret, "unlink failed sem B");


    return 0;
}