I've got a program which has 10 Guest threads, 1 check-in thread, and 1 check-out thread. All threads are created using pthread_create() within my Main() method.
The whole thing runs well until the end where the Main() method is supposed to pthread_join() with the line pthread_join(desk[1], NULL); at which time a Segmentation Fault (core dumped) error is thrown.
I know it gets to that point because of the output I see in the console.
I use gcc -pthread FileName.c and ./a.out to compile and execute.
Can you see why I get an error at that point in my code?
The entire program is posted below:
//Hotel Project
//This project creates a system to simulate a hotel.
#include <semaphore.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define NUM_GUESTS 5 //10 guests
/*GLOBAL VARIABLE*/ int globalVar0; // Check-in guestID
/*GLOBAL VARIABLE*/ int globalVar1; // Check-out guestID
/*GLOBAL VARIABLE*/ int globalVar2; // Check-out room
void *CheckIn(void *); // the two threads
void *CheckOut(void *);
pthread_t guests[NUM_GUESTS];
pthread_t desk[2];
sem_t roomSem; //total number of rooms in the hotel
sem_t check_in, check_out; //reception desks
sem_t s1, s2, s3, s4, s5, s6; //global semaphores
sem_t roomArraySem;
sem_t randSem;
int rooms[5] = {1,1,1,1,1}; //keep track of availability of each room
int total_guests; //incremented with each guest check-out
int pool; //incremented with each guest use pool
int resturant; //incremented with each guest use resturant
int fitness_center; //incremented with each guest use fitness center
int business_center; //incremented with each guest use business center
struct thread_data
{
int guest_id; // id number of guest
int room; // room guest utilizes
int event; // 0=swim, 1=resturaunt, 2=fitness, 3=business
int cost; // final cost of stay (random value)
};
struct thread_data thread_data_array[NUM_GUESTS]; // array initialization
void *Guest(void *guestData)
{
int guestid, guestroom, gevent, gcost, sleepVal;
struct thread_data *guest_data;
guest_data = (struct thread_data *) guestData;
guestid = guest_data->guest_id; // guest_id stored in struct
sem_wait(&roomSem);
/*output*/ printf("Guest %d waits for check-in\n", guestid);
sem_wait(&check_in); // if there is a room available, guest approaches check_in clerk; making him busy
/*output*/ printf("Guest %d goes to the check-in reservationist\n", guestid);
globalVar0 = guestid;
sem_post(&s1); // event ordering
sem_wait(&s2); // event ordering
guestroom = guest_data->room; // gets room value from struct
/*output*/ printf("Guest %d receives Room %d and completes check-in\n", guestid, guestroom);
sem_post(&check_in); // event ordering. Check-In now available
sem_wait(&randSem);
gevent = getRandomLessThan(4); // activity connected to 0, 1, 2, 3
printf("\tEvent: %d\n", gevent);
sem_post(&randSem);
printf("Guest: %d\tEvent: %d\n", guestid, gevent);
guest_data[guestid].event = gevent; // assign to Guest's struct
switch(gevent)
{
case(0):
/*output*/ printf("Guest %d: Go to hotel swimming pool\n", guestid);
pool++;
break;
case(1):
/*output*/ printf("Guest %d: Go to hotel resturant\n", guestid);
resturant++;
break;
case(2):
/*output*/ printf("Guest %d: Go to hotel fitness center\n", guestid);
fitness_center++;
break;
case(3):
/*output*/ printf("Guest %d: Go to hotel business center\n", guestid);
business_center++;
break;
}
sem_wait(&randSem);
sleepVal = getRandomLessThan(3) + 1;
printf("\tSleepVal: %d\n", sleepVal);
sem_post(&randSem);
printf("Guest %d sleeps for %d seconds\n", guestid, sleepVal);
sleep(1); // 0-2 + 1 = 1-3 //Change back
/*output*/ printf("Guest %d waits for check-out\n", guestid);
sem_wait(&check_out); // guest waits for check-out desk to be available
/*output*/ printf("Guest %d goes to the check-out reservationist and returns room %d\n", guestid, guestroom);
globalVar1 = guestid;
//globalVar2 = guestroom;
sem_post(&s3); // event ordering
sem_wait(&s4); // event ordering
gcost = guest_data[guestid].cost;
/*output*/ printf("Guest %d receives the total balance of $%d\n", guestid, gcost);
/*output*/ printf("Guest %d makes a payment\n", guestid);
sem_post(&s5); // event ordering
sem_wait(&s6); // event ordering
sem_post(&check_out);
total_guests++;
pthread_exit(NULL);
}
int getRandomLessThan(int x)
{
int r = -1;
srand(time(NULL));
r = rand() % x;
//printf("\tRandom number: %d\n", r);
return r;
}
int GetOpenRoom()
{
int i;
for (i=0; i<5; i++) // rooms.size and rooms.length throw errors
{
if (rooms[i] == 1) // room available
{
rooms[i] = 0; // set to unavailable
return i;
}
}
}
int RoomAvailable()
{
int i;
for (i=0; i<5; i++)
{
if (rooms[i] == 1) // room available
return 1;
}
return 0; // if none available, return 0
}
void *CheckIn(void *guestData)
{
int i, guestid, guestroom;
for(i=0; i<NUM_GUESTS; i++)
{
sem_wait(&s1); // event ordering
guestid = globalVar0; // get the global variable set to the guestID
/*output*/ printf("The check-in reservationist greets Guest %d\n", guestid);
sem_wait(&roomArraySem);
guestroom = GetOpenRoom(); // method returns index of open room
sem_post(&roomArraySem);
thread_data_array[guestid].room = guestroom; // assign room to guest
/*output*/ printf("Assign room %d to Guest %d\n", guestroom, guestid);
sem_post(&s2); // event ordering
}
pthread_exit(NULL);
}
void *CheckOut(void *guestData)
{
int i, guestid, guestroom, gcost;
for(i=0; i<NUM_GUESTS; i++)
{
sem_wait(&s3); // event ordering
guestid = globalVar1;
//guestroom = globalVar2;
guestroom = thread_data_array[guestid].room;
/*output*/ printf("The check-out greets Guest %d and receives the key from room %d\n", guestid, guestroom);
sem_wait(&roomArraySem);
rooms[guestroom] = 1; // room now available, set back to 1
sem_post(&roomArraySem);
sem_post(&roomSem); // release a room
/*output*/ printf("Calculate the balance for Guest %d\n", guestid);
gcost = getRandomLessThan(300) + 50; // 50 < cost < 350
thread_data_array[guestid].cost = gcost;
sem_post(&s4); // event ordering
sem_wait(&s5); // event ordering
/*output*/ printf("Receive $%d from Guest %d and complete the check-out\n", gcost, guestid);
sem_post(&s6); // event ordering
}
pthread_exit(NULL);
}
int main (int argc, char *argv[])
{
int rc, rc1, rc2;
int guest;
int check;
//struct thread_data *guest_data; //delete?
sem_init(&roomSem, 1, 5); //not 0 means shared between multiple processes, 5 is initial value
sem_init(&check_in, 1, 1);
sem_init(&check_out, 1, 1);
sem_init(&s1, 1, 0);
sem_init(&s2, 1, 0);
sem_init(&s3, 1, 0);
sem_init(&s4, 1, 0);
sem_init(&s5, 1, 0);
sem_init(&s6, 1, 0);
sem_init(&roomArraySem, 1, 1);
sem_init(&randSem, 1, 1);
rc1 = pthread_create(&desk[0], NULL, CheckIn, NULL); // Check In runs on it's own now
rc2 = pthread_create(&desk[1], NULL, CheckOut, NULL); // Check Out runs on it's own now
if(rc1){
printf("ERROR; return code from desk0 is %d\n\n", rc);
exit(-1);
}
if(rc2){
printf("ERROR; return code from desk1 is %d\n\n", rc);
exit(-1);
}
for(guest = 0; guest < NUM_GUESTS; guest++)
{
thread_data_array[guest].guest_id = guest; // guest ID for each guest thread
/*Output*/printf("Main(): Creating Thread: %d\n", guest);
rc = pthread_create(&guests[guest], NULL, Guest, (void *)&thread_data_array[guest]); //Guest method, &thread_data_array[guest] argument
if (rc) {
printf("ERROR; return code from pthread_create(Guest) is %d\n", rc);
exit(-1);
}
}
printf("\tDONE WITH THREADS\n");
for(guest = 0; guest < NUM_GUESTS; guest++)
{
pthread_join(guests[guest], NULL); // waits for each guest to complete and cleans memory space
}
printf("\tBETWEEN THREAD JOINS 1\n");
pthread_join(desk[0], NULL);
printf("\tBETWEEN THREAD JOINS 2\n");
pthread_join(desk[1], NULL);
printf("\tBETWEEN THREAD JOINS 3\n");
printf("\t\tNumber of Customers\n");
printf("Total Guests:\t\t%d\n", total_guests);
printf("Pool:\t\t\t%d\n", pool);
printf("Resturant:\t\t%d\n", resturant);
printf("Fitness Center:\t\t%d\n", fitness_center);
printf("Business Center:\t%d\n", business_center);
sem_close(&roomSem);
sem_close(&check_in);
sem_close(&check_out);
sem_close(&s1);
sem_close(&s2);
sem_close(&s3);
sem_close(&s4);
sem_close(&s5);
sem_close(&s6);
sem_close(&roomArraySem);
sem_close(&randSem);
}
Here's what the console returns:
tames@lab17:~/Desktop/project2$ gcc -pthread HotelProject_v4.c
tames@lab17:~/Desktop/project2$ ./a.out
Main(): Creating Thread: 0
Main(): Creating Thread: 1
Main(): Creating Thread: 2
Guest 1 waits for check-in
Main(): Creating Thread: 3
Guest 1 goes to the check-in reservationist
Main(): Creating Thread: 4
Guest 3 waits for check-in
The check-in reservationist greets Guest 1
Assign room 0 to Guest 1
Guest 2 waits for check-in
Guest 1 receives Room 0 and completes check-in
Guest 0 waits for check-in
Main(): Creating Thread: 5
Guest 4 waits for check-in
Guest 5 waits for check-in
Guest 3 goes to the check-in reservationist
Guest 1: Go to hotel fitness center
Guest 1 sleeps for 1 seconds
The check-in reservationist greets Guest 3
Assign room 1 to Guest 3
Main(): Creating Thread: 6
Guest 3 receives Room 1 and completes check-in
Main(): Creating Thread: 7
Guest 3: Go to hotel fitness center
Main(): Creating Thread: 8
Guest 6 waits for check-in
Guest 3 sleeps for 1 seconds
Guest 2 goes to the check-in reservationist
Guest 7 waits for check-in
Main(): Creating Thread: 9
Guest 8 waits for check-in
DONE WITH THREADS
The check-in reservationist greets Guest 2
Assign room 2 to Guest 2
Guest 9 waits for check-in
Guest 2 receives Room 2 and completes check-in
Guest 2: Go to hotel fitness center
Guest 0 goes to the check-in reservationist
The check-in reservationist greets Guest 0
Assign room 3 to Guest 0
Guest 2 sleeps for 1 seconds
Guest 0 receives Room 3 and completes check-in
Guest 4 goes to the check-in reservationist
Guest 0: Go to hotel fitness center
The check-in reservationist greets Guest 4
Assign room 4 to Guest 4
Guest 0 sleeps for 1 seconds
Guest 4 receives Room 4 and completes check-in
Guest 4: Go to hotel fitness center
Guest 5 goes to the check-in reservationist
Guest 4 sleeps for 1 seconds
Guest 1 waits for check-out
Guest 1 goes to the check-out reservationist and returns room 0
The check-out greets Guest 1 and receives the key from room 0
Calculate the balance for Guest 1
The check-in reservationist greets Guest 5
Assign room 0 to Guest 5
Guest 1 receives the total balance of $0
Guest 1 makes a payment
Guest 5 receives Room 0 and completes check-in
Guest 5: Go to hotel fitness center
Guest 6 goes to the check-in reservationist
Receive $58 from Guest 1 and complete the check-out
Guest 5 sleeps for 2 seconds
Guest 3 waits for check-out
Guest 3 goes to the check-out reservationist and returns room 1
The check-out greets Guest 3 and receives the key from room 1
Calculate the balance for Guest 3
The check-in reservationist greets Guest 6
Assign room 1 to Guest 6
Guest 3 receives the total balance of $0
Guest 3 makes a payment
Guest 6 receives Room 1 and completes check-in
Guest 2 waits for check-out
Receive $58 from Guest 3 and complete the check-out
Guest 7 goes to the check-in reservationist
Guest 2 goes to the check-out reservationist and returns room 2
Guest 6: Go to hotel fitness center
The check-out greets Guest 2 and receives the key from room 2
Calculate the balance for Guest 2
Guest 0 waits for check-out
Guest 6 sleeps for 2 seconds
The check-in reservationist greets Guest 7
Guest 2 receives the total balance of $0
Guest 2 makes a payment
Assign room 2 to Guest 7
Receive $58 from Guest 2 and complete the check-out
Guest 7 receives Room 2 and completes check-in
Guest 7: Go to hotel fitness center
Guest 8 goes to the check-in reservationist
Guest 7 sleeps for 2 seconds
Guest 0 goes to the check-out reservationist and returns room 3
Guest 4 waits for check-out
The check-out greets Guest 0 and receives the key from room 3
Calculate the balance for Guest 0
Guest 0 receives the total balance of $58
Guest 0 makes a payment
Receive $58 from Guest 0 and complete the check-out
The check-in reservationist greets Guest 8
Assign room 3 to Guest 8
Guest 4 goes to the check-out reservationist and returns room 4
Guest 8 receives Room 3 and completes check-in
Guest 8: Go to hotel fitness center
Guest 9 goes to the check-in reservationist
Guest 8 sleeps for 2 seconds
The check-out greets Guest 4 and receives the key from room 4
Calculate the balance for Guest 4
The check-in reservationist greets Guest 9
Assign room 4 to Guest 9
Guest 4 receives the total balance of $0
Guest 4 makes a payment
Guest 9 receives Room 4 and completes check-in
Receive $58 from Guest 4 and complete the check-out
Guest 9: Go to hotel fitness center
Guest 9 sleeps for 2 seconds
Guest 5 waits for check-out
Guest 5 goes to the check-out reservationist and returns room 0
The check-out greets Guest 5 and receives the key from room 0
Calculate the balance for Guest 5
Guest 5 receives the total balance of $0
Guest 5 makes a payment
Receive $293 from Guest 5 and complete the check-out
Guest 6 waits for check-out
Guest 6 goes to the check-out reservationist and returns room 1
Guest 7 waits for check-out
The check-out greets Guest 6 and receives the key from room 1
Calculate the balance for Guest 6
Guest 6 receives the total balance of $0
Guest 6 makes a payment
Receive $293 from Guest 6 and complete the check-out
Guest 8 waits for check-out
Guest 7 goes to the check-out reservationist and returns room 2
Guest 9 waits for check-out
The check-out greets Guest 7 and receives the key from room 2
Calculate the balance for Guest 7
Guest 7 receives the total balance of $32604
Guest 7 makes a payment
Receive $293 from Guest 7 and complete the check-out
Guest 8 goes to the check-out reservationist and returns room 3
The check-out greets Guest 8 and receives the key from room 3
Calculate the balance for Guest 8
Guest 8 receives the total balance of $0
Guest 8 makes a payment
Receive $293 from Guest 8 and complete the check-out
Guest 9 goes to the check-out reservationist and returns room 4
The check-out greets Guest 9 and receives the key from room 4
Calculate the balance for Guest 9
Guest 9 receives the total balance of $0
Guest 9 makes a payment
Receive $293 from Guest 9 and complete the check-out
BETWEEN THREAD JOINS 1
BETWEEN THREAD JOINS 2
Segmentation fault (core dumped)
