path: root/sysdeps/pthread/aio_misc.c

/* Handle general operations.
   Copyright (C) 1997-2014 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.

   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
   <http://www.gnu.org/licenses/>.  */

#include <aio.h>
#include <assert.h>
#include <errno.h>
#include <limits.h>
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <aio_misc.h>

#ifndef aio_create_helper_thread
# define aio_create_helper_thread __aio_create_helper_thread

extern inline int
__aio_create_helper_thread (pthread_t *threadp, void *(*tf) (void *), void *arg)
{
  pthread_attr_t attr;

  /* Make sure the thread is created detached.  */
  pthread_attr_init (&attr);
  pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);

  int ret = pthread_create (threadp, &attr, tf, arg);

  (void) pthread_attr_destroy (&attr);
  return ret;
}
#endif

static void add_request_to_runlist (struct requestlist *newrequest);

/* Pool of request list entries.  */
static struct requestlist **pool;

/* Number of total and allocated pool entries.  */
static size_t pool_max_size;
static size_t pool_size;

/* We implement a two dimensional array but allocate each row separately.
   The macro below determines how many entries should be used per row.
   It should better be a power of two.  */
#define ENTRIES_PER_ROW	32

/* How many rows we allocate at once.  */
#define ROWS_STEP	8

/* List of available entries.  */
static struct requestlist *freelist;

/* List of request waiting to be processed.  */
static struct requestlist *runlist;

/* Structure list of all currently processed requests.  */
static struct requestlist *requests;

/* Number of threads currently running.  */
static int nthreads;

/* Number of threads waiting for work to arrive. */
static int idle_thread_count;


/* These are the values used to optimize the use of AIO.  The user can
   overwrite them by using the `aio_init' function.  */
static struct aioinit optim =
{
  20,	/* int aio_threads;	Maximal number of threads.  */
  64,	/* int aio_num;		Number of expected simultaneous requests. */
  0,
  0,
  0,
  0,
  1,
  0
};


/* Since the list is global we need a mutex protecting it.  */
pthread_mutex_t __aio_requests_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;

/* When you add a request to the list and there are idle threads present,
   you signal this condition variable. When a thread finishes work, it waits
   on this condition variable for a time before it actually exits. */
pthread_cond_t __aio_new_request_notification = PTHREAD_COND_INITIALIZER;


/* Functions to handle request list pool.  */
static struct requestlist *
get_elem (void)
{
  struct requestlist *result;

  if (freelist == NULL)
    {
      struct requestlist *new_row;
      int cnt;

      assert (sizeof (struct aiocb) == sizeof (struct aiocb64));

      if (pool_size + 1 >= pool_max_size)
	{
	  size_t