rt/aio_suspend.c

   1 /* Suspend until termination of a requests.
   2    Copyright (C) 1997, 1998, 1999 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21
  22 /* We use an UGLY hack to prevent gcc from finding us cheating.  The
  23    implementation of aio_suspend and aio_suspend64 are identical and so
  24    we want to avoid code duplication by using aliases.  But gcc sees
  25    the different parameter lists and prints a warning.  We define here
  26    a function so that aio_suspend64 has no prototype.  */
  27 #define aio_suspend64 XXX
  28 #include <aio.h>
  29 /* And undo the hack.  */
  30 #undef aio_suspend64
  31
  32 #include <errno.h>
  33
  34 #include "aio_misc.h"
  35
  36
  37 int
  38 aio_suspend (list, nent, timeout)
  39      const struct aiocb *const list[];
  40      int nent;
  41      const struct timespec *timeout;
  42 {
  43   struct waitlist waitlist[nent];
  44   struct requestlist *requestlist[nent];
  45   pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  46   int cnt;
  47   int result = 0;
  48   int dummy;
  49   int none = 1;
  50
  51   /* Request the mutex.  */
  52   pthread_mutex_lock (&__aio_requests_mutex);
  53
  54   /* There is not yet a finished request.  Signal the request that
  55      we are working for it.  */
  56   for (cnt = 0; cnt < nent; ++cnt)
  57     if (list[cnt] != NULL && list[cnt]->__error_code == EINPROGRESS)
  58       {
  59         requestlist[cnt] = __aio_find_req ((aiocb_union *) list[cnt]);
  60
  61         if (requestlist[cnt] != NULL)
  62           {
  63             waitlist[cnt].cond = &cond;
  64             waitlist[cnt].next = requestlist[cnt]->waiting;
  65             waitlist[cnt].counterp = &dummy;
  66             waitlist[cnt].sigevp = NULL;
  67             waitlist[cnt].caller_pid = 0;       /* Not needed.  */
  68             requestlist[cnt]->waiting = &waitlist[cnt];
  69             none = 0;
  70           }
  71       }
  72
  73   /* If there is a not finished request wait for it.  */
  74   if (!none)
  75     {
  76       int oldstate;
  77
  78       /* Since `pthread_cond_wait'/`pthread_cond_timedwait' are cancelation
  79          points we must be careful.  We added entries to the waiting lists
  80          which we must remove.  So defer cancelation for now.  */
  81       pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &oldstate);
  82
  83       if (timeout == NULL)
  84         result = pthread_cond_wait (&cond, &__aio_requests_mutex);
  85       else
  86         result = pthread_cond_timedwait (&cond, &__aio_requests_mutex,
  87                                          timeout);
  88
  89       /* Now remove the entry in the waiting list for all requests
  90          which didn't terminate.  */
  91       for (cnt = 0; cnt < nent; ++cnt)
  92         if (list[cnt] != NULL && list[cnt]->__error_code == EINPROGRESS
  93             && requestlist[cnt] != NULL)
  94           {
  95             struct waitlist **listp = &requestlist[cnt]->waiting;
  96
  97             /* There is the chance that we cannot find our entry anymore.
  98                This could happen if the request terminated and restarted
  99                again.  */
 100             while (*listp != NULL && *listp != &waitlist[cnt])
 101               listp = &(*listp)->next;
 102
 103             if (*listp != NULL)
 104               *listp = (*listp)->next;
 105           }
 106
 107       /* Now it's time to restore the cancelation state.  */
 108       pthread_setcancelstate (oldstate, NULL);
 109
 110       /* Release the conditional variable.  */
 111       if (pthread_cond_destroy (&cond) != 0)
 112         /* This must never happen.  */
 113         abort ();
 114
 115       if (result != 0)
 116         {
 117           /* An error occurred.  Possibly it's EINTR.  We have to translate
 118              the timeout error report of `pthread_cond_timedwait' to the
 119              form expected from `aio_suspend'.  */
 120           if (result == ETIMEDOUT)
 121             __set_errno (EAGAIN);
 122
 123           result = -1;
 124         }
 125     }
 126
 127   /* Release the mutex.  */
 128   pthread_mutex_unlock (&__aio_requests_mutex);
 129
 130   return result;
 131 }
 132
 133 weak_alias (aio_suspend, aio_suspend64)