glibc/sysdeps/pthread/tst-fopen-threaded.c

/* Test for fread and fwrite with multiple threads.
   Copyright (C) 2025 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>. */

/* Description of test intent.
   The test creates NUM_THREADS threads for reading and writing to the
   prepared file.  The prepared file contains 'NUM_THREADS - 1' bytes
   where each byte is unique number from 0 to 'NUM_THREADS - 2'.  If all
   operations are correctly multi-threaded safe then all concurent read
   operations should succeed and read a unique 1 byte value.  The last
   thread to read should get an EOF.  In concurrent write, all write
   operations should succeed and the file should contain all unique 1
   byte values from 0 to 'NUM_THREADS - 1'.  Both concurrent read and
   concurrent write tests are repeated ITERS times to increase
   the probability of detecting concurrency issues.  */

#include <errno.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <support/check.h>
#include <support/temp_file.h>
#include <support/xstdio.h>
#include <support/xthread.h>

#define NUM_THREADS 100
#define ITERS 10

char *temp_file;
pthread_barrier_t barrier;

struct thread_data
{
  FILE *fd;
  /* Read value or value to be written.  */
  unsigned char value;
  bool eof;
};

static void *
threadReadRoutine (void *argv)
{
  struct thread_data *my_data;
  unsigned char read_buffer;
  int ret = 0;
  my_data = (struct thread_data *) argv;
  /* Wait for all threads to be ready to read.  */
  xpthread_barrier_wait (&barrier);

  ret =
    fread (&read_buffer, sizeof (char), sizeof (read_buffer), my_data->fd);
  if (feof (my_data->fd) != 0)
    {
      clearerr (my_data->fd);
      my_data->eof = true;
    }
  else
    {
      TEST_COMPARE (ret, 1);
      /* Save the read value.  */
      my_data->value = read_buffer;
    }
  TEST_COMPARE (ferror (my_data->fd), 0);
  return NULL;
}

void *
threadWriteRoutine (void *argv)
{
  struct thread_data *my_data;
  int ret = 0;
  my_data = (struct thread_data *) argv;
  /* Wait for all threads to be ready to write.  */
  xpthread_barrier_wait (&barrier);

  ret = fwrite (&my_data->value, sizeof (unsigned char), 1, my_data->fd);
  TEST_COMPARE (ferror (my_data->fd), 0);
  TEST_COMPARE (feof (my_data->fd), 0);
  TEST_COMPARE (ret, 1);
  return NULL;
}

void *
threadOpenCloseRoutine (void *argv)
{
  /* Wait for all threads to be ready to call fopen and fclose.  */
  xpthread_barrier_wait (&barrier);

  FILE *fd = xfopen ("/tmp/openclosetest", "w+");
  xfclose (fd);
  return NULL;
}

static int
do_test (void)
{
  FILE *fd_file = NULL;
  unsigned char buffer[NUM_THREADS] = "0";
  size_t ret = 0;
  pthread_t threads[NUM_THREADS];
  struct thread_data thread_data_array[NUM_THREADS];
  bool present_values[NUM_THREADS] = { false };

  /* Prepare files.  */
  for (int i = 0; i < NUM_THREADS; i++)
    buffer[i] = i;
  int fd = create_temp_file ("tst-fopen.", &temp_file);
  TEST_VERIFY_EXIT (fd != -1);
  fd_file = fdopen (fd, "w");
  /* NUM_THREADS - 1: last thread will read EOF */
  ret = fwrite (buffer, sizeof (unsigned char), NUM_THREADS - 1, fd_file);
  TEST_COMPARE (ret, NUM_THREADS - 1);
  xfclose (fd_file);

  /* Test 1: Concurrent read.  */
  for (int reps = 1; reps <= ITERS; reps++)
    {
      fd_file = xfopen (temp_file, "r");
      xpthread_barrier_init (&barrier, NULL, NUM_THREADS);
      for (int i = 0; i < NUM_THREADS; i++)
        {
          thread_data_array[i].fd = fd_file;
          /* Initialize with highest possible value so it's easier to debug if
             anything goes wrong.  */
          thread_data_array[i].value = 255;
          thread_data_array[i].eof = false;

          threads[i] =
            xpthread_create (support_small_stack_thread_attribute (),
                             threadReadRoutine,
                             (void *) &thread_data_array[i]);
        }

      for (int i = 0; i < NUM_THREADS; i++)
        {
          xpthread_join (threads[i]);
        }
      xpthread_barrier_destroy (&barrier);
      xfclose (fd_file);

      /* Verify read values.  */
      int eof_cnt = 0;
      for (int i = 0; i < NUM_THREADS; i++)
        present_values[i] = false;
      for (int i = 0; i < NUM_THREADS; i++)
        {
          if (thread_data_array[i].eof)
            {
              /* EOF was read.  */
              present_values[NUM_THREADS - 1] = true;
              eof_cnt++;
            }
          else
            {
              /* The same value shouldn't be read twice.  */
              TEST_VERIFY (!present_values[thread_data_array[i].value]);
              present_values[thread_data_array[i].value] = true;
            }
        }
      /* EOF is read exactly once.  */
      TEST_COMPARE (eof_cnt, 1);
      for (int i = 0; i < NUM_THREADS; i++)
        {
          /* All values should be read.  */
          TEST_VERIFY (present_values[i]);
        }
    }

  /* Test 2: Concurrent write.  */
  for (int reps = 1; reps <= ITERS; reps++)
    {
      fd_file = xfopen (temp_file, "w");
      xpthread_barrier_init (&barrier, NULL, NUM_THREADS);
      for (int i = 0; i < NUM_THREADS; i++)
        {
          thread_data_array[i].fd = fd_file;
          thread_data_array[i].value = i;

          threads[i] =
            xpthread_create (support_small_stack_thread_attribute (),
                             threadWriteRoutine,
                             (void *) &thread_data_array[i]);
        }

      for (int i = 0; i < NUM_THREADS; i++)
        {
          xpthread_join (threads[i]);
        }
      xpthread_barrier_destroy (&barrier);
      xfclose (fd_file);

      /* Verify written values.  */
      for (int i = 0; i < NUM_THREADS; i++)
        present_values[i] = false;
      memset (buffer, 0, NUM_THREADS);
      fd_file = xfopen (temp_file, "r");
      ret = fread (buffer, sizeof (unsigned char), NUM_THREADS, fd_file);
      TEST_COMPARE (ret, NUM_THREADS);
      for (int i = 0; i < NUM_THREADS; i++)
        {
          /* The same value shouldn't be written twice.  */
          TEST_VERIFY (!present_values[buffer[i]]);
          present_values[buffer[i]] = true;
        }
      for (int i = 0; i < NUM_THREADS; i++)
        {
          /* All values should be written.  */
          TEST_VERIFY (present_values[i]);
        }
      xfclose (fd_file);
    }

  /* Test 3: Concurrent open/close.  */
  for (int reps = 1; reps <= ITERS; reps++)
    {
      xpthread_barrier_init (&barrier, NULL, NUM_THREADS);
      for (int i = 0; i < NUM_THREADS; i++)
        {
          threads[i] =
            xpthread_create (support_small_stack_thread_attribute (),
                             threadOpenCloseRoutine, NULL);
        }
      for (int i = 0; i < NUM_THREADS; i++)
        {
          xpthread_join (threads[i]);
        }
      xpthread_barrier_destroy (&barrier);
    }

  return 0;
}

#include <support/test-driver.c>