rt/aio_suspend.c

   1 /* Suspend until termination of a requests.
   2    Copyright (C) 1997, 1998, 1999, 2000 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    implementations 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 #include <stdlib.h>
  34 #include <sys/time.h>
  35
  36 #include "aio_misc.h"
  37
  38
  39 int
  40 aio_suspend (list, nent, timeout)
  41      const struct aiocb *const list[];
  42      int nent;
  43      const struct timespec *timeout;
  44 {
  45   struct waitlist waitlist[nent];
  46   struct requestlist *requestlist[nent];
  47   pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  48   int cnt;
  49   int result = 0;
  50   int dummy;
  51   int none = 1;
  52
  53   /* Request the mutex.  */
  54   pthread_mutex_lock (&__aio_requests_mutex);
  55
  56   /* There is not yet a finished request.  Signal the request that
  57      we are working for it.  */
  58   for (cnt = 0; cnt < nent; ++cnt)
  59     if (list[cnt] != NULL && list[cnt]->__error_code == EINPROGRESS)
  60       {
  61         requestlist[cnt] = __aio_find_req ((aiocb_union *) list[cnt]);
  62
  63         if (requestlist[cnt] != NULL)
  64           {
  65             waitlist[cnt].cond = &cond;
  66             waitlist[cnt].next = requestlist[cnt]->waiting;
  67             waitlist[cnt].counterp = &dummy;
  68             waitlist[cnt].sigevp = NULL;
  69             waitlist[cnt].caller_pid = 0;       /* Not needed.  */
  70             requestlist[cnt]->waiting = &waitlist[cnt];
  71             none = 0;
  72           }
  73       }
  74
  75   /* If there is a not finished request wait for it.  */
  76   if (!none)
  77     {
  78       int oldstate;
  79
  80       /* Since `pthread_cond_wait'/`pthread_cond_timedwait' are cancelation
  81          points we must be careful.  We added entries to the waiting lists
  82          which we must remove.  So defer cancelation for now.  */
  83       pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &oldstate);
  84
  85       if (timeout == NULL)
  86         result = pthread_cond_wait (&cond, &__aio_requests_mutex);
  87       else
  88         {
  89           /* We have to convert the relative timeout value into an
  90              absolute time value with pthread_cond_timedwait expects.  */
  91           struct timeval now;
  92           struct timespec abstime;
  93
  94           __gettimeofday (&now, NULL);
  95           abstime.tv_nsec = timeout->tv_nsec + now.tv_usec * 1000;
  96           abstime.tv_sec = timeout->tv_sec + now.tv_sec;
  97           if (abstime.tv_nsec >= 1000000000)
  98             {
  99               abstime.tv_nsec -= 1000000000;
 100               abstime.tv_sec += 1;
 101             }
 102
 103           result = pthread_cond_timedwait (&cond, &__aio_requests_mutex,
 104                                            &abstime);
 105         }
 106
 107       /* Now remove the entry in the waiting list for all requests
 108          which didn't terminate.  */
 109       for (cnt = 0; cnt < nent; ++cnt)
 110         if (list[cnt] != NULL && list[cnt]->__error_code == EINPROGRESS
 111             && requestlist[cnt] != NULL)
 112           {
 113             struct waitlist **listp = &requestlist[cnt]->waiting;
 114
 115             /* There is the chance that we cannot find our entry anymore.
 116                This could happen if the request terminated and restarted
 117                again.  */
 118             while (*listp != NULL && *listp != &waitlist[cnt])
 119               listp = &(*listp)->next;
 120
 121             if (*listp != NULL)
 122               *listp = (*listp)->next;
 123           }
 124
 125       /* Now it's time to restore the cancelation state.  */
 126       pthread_setcancelstate (oldstate, NULL);
 127
 128       /* Release the conditional variable.  */
 129       if (pthread_cond_destroy (&cond) != 0)
 130         /* This must never happen.  */
 131         abort ();
 132
 133       if (result != 0)
 134         {
 135           /* An error occurred.  Possibly it's EINTR.  We have to translate
 136              the timeout error report of `pthread_cond_timedwait' to the
 137              form expected from `aio_suspend'.  */
 138           if (result == ETIMEDOUT)
 139             __set_errno (EAGAIN);
 140
 141           result = -1;
 142         }
 143     }
 144
 145   /* Release the mutex.  */
 146   pthread_mutex_unlock (&__aio_requests_mutex);
 147
 148   return result;
 149 }
 150
 151 weak_alias (aio_suspend, aio_suspend64)