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#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

typedef struct {
	  int balance;
	  pthread_mutex_t balance_mutex; 
} bank_account;

typedef struct {
	  bank_account *from;
	  bank_account *to;
	  int amount;
} deposit_thr_args;

/* return negative on error */
int create_bank_account(bank_account **ba, int initial_amount) {

	  bank_account *nba = malloc(sizeof(bank_account));

	  if (nba == NULL) {
		    return -1;
	  }

	  nba->balance = initial_amount;
	  pthread_mutex_init(&nba->balance_mutex, NULL);

	  *ba = nba;

	  return 0;
}


void *deposit(void *ptr) {
	
	  deposit_thr_args *args = (deposit_thr_args *)ptr;

	  pthread_mutex_lock(&(args->from->balance_mutex));

	  /* not enough balance to transfer */
	  if (args->from->balance < args->amount) {
		    pthread_mutex_unlock(&(args->from->balance_mutex));
		    return NULL;
	  }

	  pthread_mutex_lock(&(args->to->balance_mutex));
	  args->from->balance -= args->amount;
	  args->to->balance += args->amount;

	  pthread_mutex_unlock(&(args->from->balance_mutex));
	  pthread_mutex_unlock(&(args->to->balance_mutex));

	  return NULL;
}

int main() {

	  pthread_t thr1, thr2;
	  int err;

	  bank_account *ba1, *ba2;

	  err = create_bank_account(&ba1, 1000);
	  if (err < 0) 
		    exit(err);

	  err = create_bank_account(&ba2, 1000);
	  if (err < 0) 
		    exit(err);

	  deposit_thr_args *arg1 = malloc(sizeof(deposit_thr_args));
	  deposit_thr_args *arg2 = malloc(sizeof(deposit_thr_args));

	  arg1->from = ba1;
	  arg1->to = ba2;
	  arg1->amount = 100;

	  arg2->from = ba2;
	  arg2->to = ba1;
	  arg2->amount = 100;

	  /* perform the deposit */
	  pthread_create(&thr1, NULL, deposit, (void *)arg1);
	  pthread_create(&thr2, NULL, deposit, (void *)arg2);

	  pthread_exit(NULL);

	  return 0;
}

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

typedef struct {
	  int balance;
	  pthread_mutex_t balance_mutex; 
	  unsigned int id; /* read only and should never be changed */
} bank_account;

typedef struct {
	  bank_account *from;
	  bank_account *to;
	  int amount;
} deposit_thr_args;

unsigned int global_id = 1;

/* return negative on error */
int create_bank_account(bank_account **ba, int initial_amount) {

	  bank_account *nba = malloc(sizeof(bank_account));

	  if (nba == NULL) {
		    return -1;
	  }

	  nba->balance = initial_amount;
	  pthread_mutex_init(&nba->balance_mutex, NULL);
	  nba->id = global_id++;

	  *ba = nba;

	  return 0;
}


void *deposit(void *ptr) {
	
	  deposit_thr_args *args = (deposit_thr_args *)ptr;

	  if (args->from->id == args->to->id) 
		return NULL;

	  /* ensure proper ordering for unlockinglocking */
	  if (args->from->id < args->to->id) {
		  pthread_mutex_lock(&(args->from->balance_mutex));
		  pthread_mutex_lock(&(args->to->balance_mutex));
	  } else {
		    pthread_mutex_lock(&(args->to->balance_mutex));
		    pthread_mutex_lock(&(args->from->balance_mutex));
	  }

	  /* not enough balance to transfer */
	  if (args->from->balance < args->amount) {
		    pthread_mutex_unlock(&(args->from->balance_mutex));
		    pthread_mutex_unlock(&(args->to->balance_mutex));
		    return NULL;
	  }

	  args->from->balance -= args->amount;
	  args->to->balance += args->amount;

	  pthread_mutex_unlock(&(args->from->balance_mutex));
	  pthread_mutex_unlock(&(args->to->balance_mutex));

	  return NULL;
}

int main() {

	  pthread_t thr1, thr2;
	  int err;

	  bank_account *ba1, *ba2;

	  err = create_bank_account(&ba1, 1000);
	  if (err < 0) 
		    exit(err);

	  err = create_bank_account(&ba2, 1000);
	  if (err < 0) 
		    exit(err);

	  deposit_thr_args *arg1 = malloc(sizeof(deposit_thr_args));
	  deposit_thr_args *arg2 = malloc(sizeof(deposit_thr_args));

	  arg1->from = ba1;
	  arg1->to = ba2;
	  arg1->amount = 100;

	  arg2->from = ba2;
	  arg2->to = ba1;
	  arg2->amount = 100;

	  /* perform the deposit */
	  pthread_create(&thr1, NULL, deposit, (void *)arg1);
	  pthread_create(&thr2, NULL, deposit, (void *)arg2);

	  pthread_exit(NULL);

	  return 0;
}