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Я пытаюсь реализовать первую проблему с читателями (предпочтение читателя) в C. Я использую блокировки и разблокировки мьютексов, чтобы ни один автор не мог получить доступ к потоку, если у читателя есть блокировка, и любой читатель может получить доступ к потоку, если у первого читателя есть замок. Вот мой код. Я не могу получить код до конца, т. Е. Он не достигает части соединения потока. Наверное, я где-то зашел в тупик, или, может быть, я помещаю свои блокировки мьютекса и разблокирует их в неправильном месте.Что случилось с этой первой реализацией решений для читателей-писателей в C с использованием мьютекса?
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#include <fcntl.h>
#include <sys/types.h>
#define FALSE 0
#define TRUE 1
#define SLOWNESS 30000
#define INVALID_ACCNO -99999
#define SIZE 100
#define WRITE_ITR 100000
#define READ_ITR 100000
#define MAX_BALANCE 1000000
typedef struct {
int accno;
float balance;
} account;
// sleep function
void rest()
{
usleep(100);
}
//Global shared data structure
account account_list[SIZE]; /* this is the data structure that the readers and writers will be accessing concurrently.*/
pthread_mutex_t rw_lock = PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_t r_lock = PTHREAD_MUTEX_INITIALIZER;
/* Writer thread - will update the account_list data structure.
Takes as argument the seed for the srand() function.
*/
void * writer_thr(void * arg)
{
printf("Writer thread ID %ld\n", pthread_self());
srand(*((unsigned int *) arg)); /* set random number seed for this writer */
int i, j;
int r_idx;
unsigned char found; /* For every update_acc[j], set to TRUE if found in account_list, else set to FALSE */
account update_acc[WRITE_ITR];
/* first create a random data set of account updates */
for (i = 0; i < WRITE_ITR;i++)
{
r_idx = rand() % SIZE; /* a random number in the range [0, SIZE) */
update_acc[i].accno = account_list[r_idx].accno;
update_acc[i].balance = 1000.0 + (float) (rand() % MAX_BALANCE);
}//end for
/* open a writer thread log file */
char thr_fname[64];
snprintf(thr_fname, 64, "writer_%ld_thr.log", pthread_self());
FILE* fd = fopen(thr_fname, "w");
if (!fd)
{
fprintf(stderr,"Failed to open writer log file %s\n", thr_fname);
pthread_exit(&errno);
}//end if
/* The writer thread will now try to update the shared account_list data structure.
For each entry 'j' in the update_acc[] array, it will find the corresponding
account number in the account_list array and update the balance of that account
number with the value stored in update_acc[j].
*/
int temp_accno;
for (j = 0; j < WRITE_ITR;j++) {
found = FALSE;
for (i = 0; i < SIZE;i++) {
if (account_list[i].accno == update_acc[j].accno) {
found = 1;
temp_accno = account_list[i].accno;
pthread_mutex_lock(&rw_lock);
account_list[i].accno = INVALID_ACCNO;
account_list[i].balance = update_acc[j].balance;
account_list[i].accno = temp_accno;
rest(); /* makes the write long duration - SO AS TO INTRODUCE LATENCY IN WRITE before going for next 'j' */
pthread_mutex_unlock(&rw_lock);
fprintf(fd, "Account number = %d [%d]: old balance = %6.2f, new balance = %6.2f\n",
account_list[i].accno, update_acc[j].accno, account_list[i].balance, update_acc[j].balance);
}//end if
if (!found)
fprintf(fd, "Failed to find account number %d!\n", update_acc[j].accno);
} // end test-set for-loop
}
fclose(fd);
return NULL;
}
/* Reader thread - will read the account_list data structure.
Takes as argument the seed for the srand() function.
*/
void * reader_thr(void *arg)
{
printf("Reader thread ID %ld\n", pthread_self());
srand(*((unsigned int *) arg)); /* set random number seed for this reader */
int i, j;
int r_idx;
unsigned char found; /* For every read_acc[j], set to TRUE if found in account_list, else set to FALSE */
account read_acc[READ_ITR];
/* first create a random data set of account updates */
for (i = 0; i < READ_ITR;i++)
{
r_idx = rand() % SIZE; /* a random number in the range [0, SIZE) */
read_acc[i].accno = account_list[r_idx].accno;
read_acc[i].balance = 0.0; /* we are going to read in the value */
}//end for
/* open a reader thread log file */
char thr_fname[64];
snprintf(thr_fname, 64, "reader_%ld_thr.log", pthread_self());
FILE *fd = fopen(thr_fname, "w");
if (!fd)
{
fprintf(stderr,"Failed to reader log file %s\n", thr_fname);
pthread_exit(&errno);
}//end if
/* The reader thread will now try to read the shared account_list data structure.
For each entry 'j' in the read_acc[] array, the reader will fetch the
corresponding balance from the account_list[] array and store in
read_acc[j].balance. */
for (j = 0; j < READ_ITR;j++) {
/* Now read the shared data structure */
found = FALSE;
for (i = 0; i < SIZE;i++) {
rest();
if (account_list[i].accno == read_acc[j].accno) {
found = TRUE;
fprintf(fd, "Account number = %d [%d], balance read = %6.2f\n",
account_list[i].accno, read_acc[j].accno, read_acc[j].balance);
pthread_mutex_lock(&r_lock);
if(j == 1)
{
pthread_mutex_lock(&rw_lock);
}
pthread_mutex_unlock(&r_lock);
read_acc[j].balance = account_list[i].balance;
pthread_mutex_lock(&r_lock);
if(j == READ_ITR - 1)
{
pthread_mutex_unlock(&rw_lock);
}
pthread_mutex_unlock(&r_lock);
}
if (!found)
fprintf(fd, "Failed to find account number %d!\n", read_acc[j].accno);
} // end test-set for-loop
}
fclose(fd);
return NULL;
}
/* populate the shared account_list data structure */
void create_testset() {
time_t t;
srand(time(&t));
int i;
for (i = 0;i < SIZE;i++) {
account_list[i].accno = 1000 + rand() % RAND_MAX;
account_list[i].balance = 100 + rand() % MAX_BALANCE;
}
return;
}
void usage(char *str) {
printf("Usage: %s -r <NUM_READERS> -w <NUM_WRITERS>\n", str);
return;
}
int main(int argc, char *argv[])
{
time_t t;
unsigned int seed;
int i;
int READ_THREADS; /* number of readers to create */
int WRITE_THREADS; /* number of writers to create */
if(argc <= 3)
{
usage("./rw");
exit(EXIT_FAILURE);
}
int opt;
while((opt = getopt(argc, argv, "r:w:")) != -1)
{
switch(opt)
{
case 'r':
READ_THREADS = atoi(optarg);
break;
case 'w':
WRITE_THREADS = atoi(optarg);
break;
default:
usage("./rw");
exit(EXIT_FAILURE);
}
}
pthread_t* reader_idx = (pthread_t *) malloc(sizeof(pthread_t) * READ_THREADS); /* holds thread IDs of readers */
pthread_t* writer_idx = (pthread_t *) malloc(sizeof(pthread_t) * WRITE_THREADS); /* holds thread IDs of writers */
/* create readers */
for (i = 0;i < READ_THREADS;i++)
{
seed = (unsigned int) time(&t);
if((pthread_create(&reader_idx[i], NULL, reader_thr, &seed)) != 0)
{
perror("pthread reader create");
exit(-1);
}
}
printf("Done creating reader threads!\n");
/* create writers */
for (i = 0;i < WRITE_THREADS;i++)
{
seed = (unsigned int) time(&t);
/* YOUR CODE GOES HERE */
if((pthread_create(&writer_idx[i], NULL, writer_thr, &seed)) != 0)
{
perror("pthread writer create");
exit(-1);
}
}
printf("Done creating writer threads!\n");
/* Join all reader and writer threads.
*/
for(i = 0; i < READ_THREADS; i++)
{
pthread_join(reader_idx[i], NULL);
}
for(i = 0; i < WRITE_THREADS; i++)
{
pthread_join(writer_idx[i], NULL);
}
printf("Reader threads joined.\n");
printf("Writer threads joined.\n");
pthread_mutex_destroy(&r_lock);
pthread_mutex_destroy(&rw_lock);
return 0;
}
Это много трески. Пожалуйста, найдите MCVE на SO. У вас есть доступ к отладчику? Он может иметь образовательную ценность, не помогая вам найти ошибки в программировании. – MikeC
Вы можете узнать о том, как создать MCVE, посмотрев на [MCVE] (который создается путем ввода '[MCVE]' в текст комментария). –