glibc/rt/lio_listio.c

/* Enqueue and list of read or write requests.
   Copyright (C) 1997, 1998 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 Library General Public License as
   published by the Free Software Foundation; either version 2 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <aio.h>
#include <errno.h>
#include <stdlib.h>

#include "aio_misc.h"


/* We need this special structure to handle asynchronous I/O.  */
struct async_waitlist
  {
    int counter;
    struct sigevent sigev;
    struct waitlist list[0];
  };


int
lio_listio (mode, list, nent, sig)
     int mode;
     struct aiocb *const list[];
     int nent;
     struct sigevent *sig;
{
  struct requestlist *requests[nent];
  int cnt;
  volatile int total = 0;
  int result = 0;

  /* Check arguments.  */
  if (mode != LIO_WAIT && mode != LIO_NOWAIT)
    {
      __set_errno (EINVAL);
      return -1;
    }

  /* Request the mutex.  */
  pthread_mutex_lock (&__aio_requests_mutex);

  /* Now we can enqueue all requests.  Since we already acquired the
     mutex the enqueue function need not do this.  */
  for (cnt = 0; cnt < nent; ++cnt)
    if (list[cnt] != NULL && list[cnt]->aio_lio_opcode != LIO_NOP)
      {
	requests[cnt] =  __aio_enqueue_request ((aiocb_union *) list[cnt],
						list[cnt]->aio_lio_opcode);

	if (requests[cnt] != NULL)
	  /* Successfully enqueued.  */
	  ++total;
	else
	  /* Signal that we've seen an error.  `errno' and the error code
	     of the aiocb will tell more.  */
	  result = -1;
      }

  if (total == 0)
    {
      /* We don't have anything to do except signalling if we work
	 asynchronously.  */
      if (mode == LIO_NOWAIT)
	__aio_notify_only (sig);
    }
  else if (mode == LIO_WAIT)
    {
      pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
      struct waitlist waitlist[nent];
      int oldstate;

      total = 0;
      for (cnt = 0; cnt < nent; ++cnt)
	if (list[cnt] != NULL && list[cnt]->aio_lio_opcode != LIO_NOP
	    && requests[cnt] != NULL)
	  {
	    waitlist[cnt].cond = &cond;
	    waitlist[cnt].next = requests[cnt]->waiting;
	    waitlist[cnt].counterp = NULL;
	    waitlist[cnt].sigevp = NULL;
	    requests[cnt]->waiting = &waitlist[cnt];
	    ++total;
	  }

      /* Since `pthread_cond_wait'/`pthread_cond_timedwait' are cancelation
	 points we must be careful.  We added entries to the waiting lists
	 which we must remove.  So defer cancelation for now.  */
      pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &oldstate);

      while (total > 0)
	if (pthread_cond_wait (&cond, &__aio_requests_mutex) == 0)
	  --total;

      /* Now it's time to restore the cancelation state.  */
      pthread_setcancelstate (oldstate, NULL);

      /* Release the conditional variable.  */
      if (pthread_cond_destroy (&cond) != 0)
	/* This must never happen.  */
	abort ();
    }
  else
    {
      struct async_waitlist *waitlist;

      waitlist = (struct async_waitlist *)
	malloc (sizeof (struct async_waitlist)
		+ (nent * sizeof (struct waitlist)));

      if (waitlist == NULL)
	{
	  __set_errno (EAGAIN);
	  result = -1;
	}
      else
	{
	  total = 0;

	  for (cnt = 0; cnt < nent; ++cnt)
	    if (list[cnt] != NULL && list[cnt]->aio_lio_opcode != LIO_NOP
		&& requests[cnt] != NULL)
	      {
		waitlist->list[cnt].cond = NULL;
		waitlist->list[cnt].next = requests[cnt]->waiting;
		waitlist->list[cnt].counterp = &waitlist->counter;
		waitlist->list[cnt].sigevp = &waitlist->sigev;
		requests[cnt]->waiting = &waitlist->list[cnt];
		++total;
	      }

	  waitlist->counter = total;
	  waitlist->sigev = *sig;
	}
    }

  /* Release the mutex.  */
  pthread_mutex_unlock (&__aio_requests_mutex);

  return result;
}