resolv/gai_suspend.c

   1 /* Copyright (C) 2001 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <netdb.h>
  22 #include <pthread.h>
  23 #include <stdlib.h>
  24 #include <sys/time.h>
  25
  26 #include "gai_misc.h"
  27
  28
  29 int
  30 gai_suspend (const struct gaicb *const list[], int ent,
  31              const struct timespec *timeout)
  32 {
  33   struct waitlist waitlist[ent];
  34   struct requestlist *requestlist[ent];
  35   pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  36   int cnt;
  37   int dummy;
  38   int none = 1;
  39   int result;
  40
  41   /* Request the mutex.  */
  42   pthread_mutex_lock (&__gai_requests_mutex);
  43
  44   /* There is not yet a finished request.  Signal the request that
  45      we are working for it.  */
  46   for (cnt = 0; cnt < ent; ++cnt)
  47     if (list[cnt] != NULL && list[cnt]->__return == EAI_INPROGRESS)
  48       {
  49         requestlist[cnt] = __gai_find_request (list[cnt]);
  50
  51         if (requestlist[cnt] != NULL)
  52           {
  53             waitlist[cnt].cond = &cond;
  54             waitlist[cnt].next = requestlist[cnt]->waiting;
  55             waitlist[cnt].counterp = &dummy;
  56             waitlist[cnt].sigevp = NULL;
  57             waitlist[cnt].caller_pid = 0;       /* Not needed.  */
  58             requestlist[cnt]->waiting = &waitlist[cnt];
  59             none = 0;
  60           }
  61       }
  62
  63   if (none)
  64     {
  65       if (cnt < ent)
  66         /* There is an entry which is finished.  */
  67         result = 0;
  68       else
  69         result = EAI_ALLDONE;
  70     }
  71   else
  72     {
  73       /* There is no request done but some are still being worked on.  */
  74       int oldstate;
  75
  76       /* Since `pthread_cond_wait'/`pthread_cond_timedwait' are cancelation
  77          points we must be careful.  We added entries to the waiting lists
  78          which we must remove.  So defer cancelation for now.  */
  79       pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &oldstate);
  80
  81       if (timeout == NULL)
  82         result = pthread_cond_wait (&cond, &__gai_requests_mutex);
  83       else
  84         {
  85           /* We have to convert the relative timeout value into an
  86              absolute time value with pthread_cond_timedwait expects.  */
  87           struct timeval now;
  88           struct timespec abstime;
  89
  90           __gettimeofday (&now, NULL);
  91           abstime.tv_nsec = timeout->tv_nsec + now.tv_usec * 1000;
  92           abstime.tv_sec = timeout->tv_sec + now.tv_sec;
  93           if (abstime.tv_nsec >= 1000000000)
  94             {
  95               abstime.tv_nsec -= 1000000000;
  96               abstime.tv_sec += 1;
  97             }
  98
  99           result = pthread_cond_timedwait (&cond, &__gai_requests_mutex,
 100                                            &abstime);
 101         }
 102
 103       /* Now remove the entry in the waiting list for all requests
 104          which didn't terminate.  */
 105       for (cnt = 0; cnt < ent; ++cnt)
 106         if (list[cnt] != NULL && list[cnt]->__return == EAI_INPROGRESS
 107             && requestlist[cnt] != NULL)
 108           {
 109             struct waitlist **listp = &requestlist[cnt]->waiting;
 110
 111             /* There is the chance that we cannot find our entry anymore.
 112                This could happen if the request terminated and restarted
 113                again.  */
 114             while (*listp != NULL && *listp != &waitlist[cnt])
 115               listp = &(*listp)->next;
 116
 117             if (*listp != NULL)
 118               *listp = (*listp)->next;
 119           }
 120
 121       /* Now it's time to restore the cancelation state.  */
 122       pthread_setcancelstate (oldstate, NULL);
 123
 124       /* Release the conditional variable.  */
 125       if (pthread_cond_destroy (&cond) != 0)
 126         /* This must never happen.  */
 127         abort ();
 128
 129       if (result != 0)
 130         {
 131           /* An error occurred.  Possibly it's EINTR.  We have to translate
 132              the timeout error report of `pthread_cond_timedwait' to the
 133              form expected from `gai_suspend'.  */
 134           if (__builtin_expect (result, ETIMEDOUT) == ETIMEDOUT)
 135             result = EAI_AGAIN;
 136           else if (result == EINTR)
 137             result = EAI_INTR;
 138           else
 139             result = EAI_SYSTEM;
 140         }
 141     }
 142
 143   /* Release the mutex.  */
 144   pthread_mutex_unlock (&__gai_requests_mutex);
 145
 146   return result;
 147 }