resolv/gai_suspend.c

   1 /* Copyright (C) 2001-2017 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <netdb.h>
  21 #include <pthread.h>
  22 #include <stdlib.h>
  23 #include <sys/time.h>
  24
  25 #include <gai_misc.h>
  26
  27
  28 int
  29 gai_suspend (const struct gaicb *const list[], int ent,
  30              const struct timespec *timeout)
  31 {
  32   struct waitlist waitlist[ent];
  33   struct requestlist *requestlist[ent];
  34 #ifndef DONT_NEED_GAI_MISC_COND
  35   pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
  36 #endif
  37   int cnt;
  38   unsigned int cntr = 1;
  39   int none = 1;
  40   int result;
  41
  42   /* Request the mutex.  */
  43   pthread_mutex_lock (&__gai_requests_mutex);
  44
  45   /* There is not yet a finished request.  Signal the request that
  46      we are working for it.  */
  47   for (cnt = 0; cnt < ent; ++cnt)
  48     if (list[cnt] != NULL && list[cnt]->__return == EAI_INPROGRESS)
  49       {
  50         requestlist[cnt] = __gai_find_request (list[cnt]);
  51
  52         if (requestlist[cnt] != NULL)
  53           {
  54 #ifndef DONT_NEED_GAI_MISC_COND
  55             waitlist[cnt].cond = &cond;
  56 #endif
  57             waitlist[cnt].next = requestlist[cnt]->waiting;
  58             waitlist[cnt].counterp = &cntr;
  59             waitlist[cnt].sigevp = NULL;
  60             waitlist[cnt].caller_pid = 0;       /* Not needed.  */
  61             requestlist[cnt]->waiting = &waitlist[cnt];
  62             none = 0;
  63           }
  64       }
  65
  66   if (none)
  67     {
  68       if (cnt < ent)
  69         /* There is an entry which is finished.  */
  70         result = 0;
  71       else
  72         result = EAI_ALLDONE;
  73     }
  74   else
  75     {
  76       /* There is no request done but some are still being worked on.  */
  77       int oldstate;
  78
  79       /* Since `pthread_cond_wait'/`pthread_cond_timedwait' are cancelation
  80          points we must be careful.  We added entries to the waiting lists
  81          which we must remove.  So defer cancelation for now.  */
  82       pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &oldstate);
  83
  84 #ifdef DONT_NEED_GAI_MISC_COND
  85       result = 0;
  86       GAI_MISC_WAIT (result, cntr, timeout, 1);
  87 #else
  88       if (timeout == NULL)
  89         result = pthread_cond_wait (&cond, &__gai_requests_mutex);
  90       else
  91         {
  92           /* We have to convert the relative timeout value into an
  93              absolute time value with pthread_cond_timedwait expects.  */
  94           struct timeval now;
  95           struct timespec abstime;
  96
  97           __gettimeofday (&now, NULL);
  98           abstime.tv_nsec = timeout->tv_nsec + now.tv_usec * 1000;
  99           abstime.tv_sec = timeout->tv_sec + now.tv_sec;
 100           if (abstime.tv_nsec >= 1000000000)
 101             {
 102               abstime.tv_nsec -= 1000000000;
 103               abstime.tv_sec += 1;
 104             }
 105
 106           result = pthread_cond_timedwait (&cond, &__gai_requests_mutex,
 107                                            &abstime);
 108         }
 109 #endif
 110
 111       /* Now remove the entry in the waiting list for all requests
 112          which didn't terminate.  */
 113       for (cnt = 0; cnt < ent; ++cnt)
 114         if (list[cnt] != NULL && list[cnt]->__return == EAI_INPROGRESS
 115             && requestlist[cnt] != NULL)
 116           {
 117             struct waitlist **listp = &requestlist[cnt]->waiting;
 118
 119             /* There is the chance that we cannot find our entry anymore.
 120                This could happen if the request terminated and restarted
 121                again.  */
 122             while (*listp != NULL && *listp != &waitlist[cnt])
 123               listp = &(*listp)->next;
 124
 125             if (*listp != NULL)
 126               *listp = (*listp)->next;
 127           }
 128
 129       /* Now it's time to restore the cancelation state.  */
 130       pthread_setcancelstate (oldstate, NULL);
 131
 132 #ifndef DONT_NEED_GAI_MISC_COND
 133       /* Release the conditional variable.  */
 134       if (pthread_cond_destroy (&cond) != 0)
 135         /* This must never happen.  */
 136         abort ();
 137 #endif
 138
 139       if (result != 0)
 140         {
 141           /* An error occurred.  Possibly it's EINTR.  We have to translate
 142              the timeout error report of `pthread_cond_timedwait' to the
 143              form expected from `gai_suspend'.  */
 144           if (__builtin_expect (result, ETIMEDOUT) == ETIMEDOUT)
 145             result = EAI_AGAIN;
 146           else if (result == EINTR)
 147             result = EAI_INTR;
 148           else
 149             result = EAI_SYSTEM;
 150         }
 151     }
 152
 153   /* Release the mutex.  */
 154   pthread_mutex_unlock (&__gai_requests_mutex);
 155
 156   return result;
 157 }