resolv/gai_notify.c

   1 /* Copyright (C) 2001-2020 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <netdb.h>
  20 #include <pthread.h>
  21 #include <stdlib.h>
  22 #include <gai_misc.h>
  23
  24
  25 struct notify_func
  26   {
  27     void (*func) (sigval_t);
  28     sigval_t value;
  29   };
  30
  31 static void *
  32 notify_func_wrapper (void *arg)
  33 {
  34   gai_start_notify_thread ();
  35   struct notify_func *const n = arg;
  36   void (*func) (sigval_t) = n->func;
  37   sigval_t value = n->value;
  38   free (n);
  39   (*func) (value);
  40   return NULL;
  41 }
  42
  43
  44 int
  45 __gai_notify_only (struct sigevent *sigev, pid_t caller_pid)
  46 {
  47   int result = 0;
  48
  49   /* Send the signal to notify about finished processing of the request.  */
  50   if (sigev->sigev_notify == SIGEV_THREAD)
  51     {
  52       /* We have to start a thread.  */
  53       pthread_t tid;
  54       pthread_attr_t attr, *pattr;
  55
  56       pattr = (pthread_attr_t *) sigev->sigev_notify_attributes;
  57       if (pattr == NULL)
  58         {
  59           pthread_attr_init (&attr);
  60           pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
  61           pattr = &attr;
  62         }
  63
  64       /* SIGEV may be freed as soon as we return, so we cannot let the
  65          notification thread use that pointer.  Even though a sigval_t is
  66          only one word and the same size as a void *, we cannot just pass
  67          the value through pthread_create as the argument and have the new
  68          thread run the user's function directly, because on some machines
  69          the calling convention for a union like sigval_t is different from
  70          that for a pointer type like void *.  */
  71       struct notify_func *nf = malloc (sizeof *nf);
  72       if (nf == NULL)
  73         result = -1;
  74       else
  75         {
  76           nf->func = sigev->sigev_notify_function;
  77           nf->value = sigev->sigev_value;
  78           if (pthread_create (&tid, pattr, notify_func_wrapper, nf) < 0)
  79             {
  80               free (nf);
  81               result = -1;
  82             }
  83         }
  84     }
  85   else if (sigev->sigev_notify == SIGEV_SIGNAL)
  86     /* We have to send a signal.  */
  87     if (__gai_sigqueue (sigev->sigev_signo, sigev->sigev_value, caller_pid)
  88         < 0)
  89       result = -1;
  90
  91   return result;
  92 }
  93
  94
  95 void
  96 __gai_notify (struct requestlist *req)
  97 {
  98   struct waitlist *waitlist;
  99
 100   /* Now also notify possibly waiting threads.  */
 101   waitlist = req->waiting;
 102   while (waitlist != NULL)
 103     {
 104       struct waitlist *next = waitlist->next;
 105
 106       if (waitlist->sigevp == NULL)
 107         {
 108 #ifdef DONT_NEED_GAI_MISC_COND
 109           GAI_MISC_NOTIFY (waitlist);
 110 #else
 111           /* Decrement the counter.  */
 112           --*waitlist->counterp;
 113
 114           pthread_cond_signal (waitlist->cond);
 115 #endif
 116         }
 117       else
 118         /* This is part of an asynchronous `getaddrinfo_a' operation.  If
 119            this request is the last one, send the signal.  */
 120         if (--*waitlist->counterp == 0)
 121           {
 122             __gai_notify_only (waitlist->sigevp, waitlist->caller_pid);
 123             /* This is tricky.  See getaddrinfo_a.c for the reason why
 124                this works.  */
 125             free ((void *) waitlist->counterp);
 126           }
 127
 128       waitlist = next;
 129     }
 130 }