why dose this thread code output differently? - c

Question

I'm trying to wrap my head wrap my head around threads, I would like to have only one direction of car on the bridge at a time at at the moment only east bound cars work. i commented out line 37's randomized+ direction function and when substituting in "east"code works as expected, but when running "west" it hold and theres my issue. Any help appreciated.
#include <signal.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#include <sys/sem.h>
#include <semaphore.h>
#define MAXCARS 5
#define MAXWAIT 10
#define CROSSINGTIME 2
int G_direction = 0;
int carNum;
int retVal=0, lower = 0, upper = 1;
int car_rid[MAXCARS];
pthread_t threads[MAXCARS];
sem_t direc_sem, car_E, car_W,bridge_sem;
const char* printRandoms() ///randomise the cars direction
{
int num = (rand() % (upper - lower + 1)) + lower;
if (num == 0){
//left headed west
return "west";
}else return "east";
//return num;
}
void *car(void *arg) {
int carNum = (int)(intptr_t)arg; //what car is it
const char* direction = "west";//printRandoms(); //random direction
printf("car no %d is idling, planning to go %s \n",carNum, direction);// test print
sleep( rand() % MAXWAIT ); // wait a random amounnt of time
sem_wait(&direc_sem);//isolate the direction value
if(strcmp(direction,"west") == 0){
if (G_direction > 0){//g_direction 1 = one car headed east 2 two headed east
sem_wait(&car_E);//if traffic flow is in the wrong direction wait for the semaphore
}
G_direction--;//->> move ON the bridge
if (G_direction == -1){//if last car on bridge lock west bound traffic
sem_wait(&car_W);
}
}
sem_post(&direc_sem);
sem_wait(&direc_sem);//isolate the direction value
if(strcmp(direction,"east") == 0){
if (G_direction < 0){//g_direction 1 = one car headed east 2 two headed east
sem_wait(&car_W);//if traffic flow is in the wrong direction wait for the semaphore
}
G_direction++;//->> move ON the bridge
if (G_direction == 1){//if last car on bridge lock west bound traffic
sem_wait(&car_E);
}
}
sem_post(&direc_sem);
printf("car no %d goes ON the bridge heading %s \n", carNum,direction);
sleep(CROSSINGTIME);
printf("car no %d goes OFF the bridge heading %s \n", carNum, direction);
sem_wait(&direc_sem);//isolate the direction value
if(strcmp(direction, "west") == 0){
G_direction++;//->> move OFF the bridge
if (G_direction == 0){//if last car on bridge unlock other traffic
sem_post(&car_W);
}
}
sem_post(&direc_sem);
sem_wait(&direc_sem);//isolate the direction value
if(strcmp(direction,"east") == 0){
G_direction--;//->> move off the bridge
if (G_direction == 0){//if last car on bridge unlock other traffic
sem_post(&car_E);
}
}
sem_post(&direc_sem);
}
int main( void ){
sem_init(&direc_sem, 0, 1);
sem_init(&car_E, 0, 1);
sem_init(&bridge_sem, 0, 1);
for (int i = 0; i < MAXCARS; i++){
retVal = pthread_create(&threads[i], NULL,car ,(void *)(intptr_t)i);
if(retVal!=0){
printf("pthread_create failed in %d_th pass\n",i);
exit(EXIT_FAILURE);
}
}
for (int i = 0; i < MAXCARS; i++){
retVal = pthread_join(threads[i], NULL);
if(retVal!=0){
printf("pthread_join failed in %d_th pass\n",i);
exit(EXIT_FAILURE);
}
}
//sem_destroy(&carLock);
return 0;
}