I am building a program for a school assignment. It has the following requirements as shown below.
Must use Mutexes
Must use Pthreads
Create 5 threads with random synchronization (aka: running in a non-specific order)
Threads must be detached from the main thread
Each thread is going to read from a file and adjust the balance of a bank account, each with different input files.
This is the link to the actual assignment and what we need to be doing with it for a slightly more detailed set of information AssignmentTxtFile
What my main question is to solve the deadlocking problem I have encounter. I do not know how to approach this problem exactly, I understand that I need to figure out a way for it not to enter into multiple thread's critical sections at any given time. How am I going to do this while keeping the execution order random?
Here is the code that I currently have for this program.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>
#include <unistd.h>
pthread_mutex_t mutex1 = PTHREAD_MUTEX_INITIALIZER;
float balance = 0;
void *thread1(void *value){
FILE *fPTR;
char buffer;
float number;
char *fileName = "data1.in";
fPTR = fopen(fileName, "r");
if (fPTR == NULL){
printf("was unable to open: %s\n", fileName);
return NULL;
}
while(1){
//Critical Section of Thread1
pthread_mutex_lock(&mutex1);
fscanf(fPTR, "%c%f\n", &buffer, &number);
if(buffer == '+'){
balance += number;
}
if(buffer == '-'){
balance -= number;
}
printf("Account balance of thread1 is: %f\n", balance);
if(feof(fPTR)){
fclose(fPTR);
printf("end of data1.in");
return NULL;
}
printf("end of while thread1\n");
pthread_mutex_unlock(&mutex1);
sleep(.3);
}
}
void *thread2(void *value){
FILE *fPTR;
char buffer;
float number;
char *fileName = "data2.in";
fPTR = fopen(fileName, "r");
if (fPTR == NULL){
printf("was unable to open: %s\n", fileName);
return NULL;
}
while(1){
//Critical Section of Thread2
pthread_mutex_lock(&mutex1);
fscanf(fPTR, "%c%f\n", &buffer, &number);
if(buffer == '+'){
balance += number;
}
if(buffer == '-'){
balance -= number;
}
printf("Account balance of thread2 is: %f\n", balance);
if(feof(fPTR)){
fclose(fPTR);
printf("end of data2.in");
return NULL;
}
printf("end of while thread2\n");
pthread_mutex_unlock(&mutex1);
sleep(.3);
}
}
void *thread3(void *value){
FILE *fPTR;
char buffer;
float number;
char *fileName = "data3.in";
fPTR = fopen(fileName, "r");
if (fPTR == NULL){
printf("was unable to open: %s\n", fileName);
return NULL;
}
while(1){
//Critical Section of Thread3
pthread_mutex_lock(&mutex1);
fscanf(fPTR, "%c%f\n", &buffer, &number);
if(buffer == '+'){
balance += number;
}
if(buffer == '-'){
balance -= number;
}
printf("Account balance of thread3 is: %f\n", balance);
if(feof(fPTR)){
fclose(fPTR);
printf("end of data3.in");
return NULL;
}
printf("end of while thread3\n");
pthread_mutex_unlock(&mutex1);
sleep(.3);
}
}
void *thread4(void *value){
FILE *fPTR;
char buffer;
float number;
char *fileName = "data4.in";
fPTR = fopen(fileName, "r");
if (fPTR == NULL){
printf("was unable to open: %s\n", fileName);
return NULL;
}
while(1){
//Critical Section of Thread4
pthread_mutex_lock(&mutex1);
fscanf(fPTR, "%c%f\n", &buffer, &number);
if(buffer == '+'){
balance += number;
}
if(buffer == '-'){
balance -= number;
}
printf("Account balance of thread4 is: %f\n", balance);
if(feof(fPTR)){
fclose(fPTR);
printf("end of data4.in");
return NULL;
}
printf("end of while thread4\n");
pthread_mutex_unlock(&mutex1);
sleep(.3);
}
}
void *thread5(void *value){
FILE *fPTR;
char buffer;
float number;
char *fileName = "data5.in";
fPTR = fopen(fileName, "r");
if (fPTR == NULL){
printf("was unable to open: %s\n", fileName);
return NULL;
}
while(1){
//Critical Section of Thread5
pthread_mutex_lock(&mutex1);
fscanf(fPTR, "%c%f\n", &buffer, &number);
if(buffer == '+'){
balance += number;
}
if(buffer == '-'){
balance -= number;
}
printf("Account balance of thread5 is: %f\n", balance);
if(feof(fPTR)){
fclose(fPTR);
printf("end of data5.in");
return NULL;
}
printf("end of while thread5\n");
pthread_mutex_unlock(&mutex1);
sleep(.3);
}
}
int main(int argc, char **argv){
pthread_t pthread1;
pthread_t pthread2;
pthread_t pthread3;
pthread_t pthread4;
pthread_t pthread5;
pthread_create(&pthread1, NULL, thread1, NULL);
pthread_create(&pthread2, NULL, thread2, NULL);
pthread_create(&pthread3, NULL, thread3, NULL);
pthread_create(&pthread4, NULL, thread4, NULL);
pthread_create(&pthread5, NULL, thread5, NULL);
pthread_detach(pthread1);
pthread_detach(pthread2);
pthread_detach(pthread3);
pthread_detach(pthread4);
pthread_detach(pthread5);
printf("main completed\n");
pthread_exit(0);
}
