resolv/gai_notify.c

   1 /* Copyright (C) 2001, 2006 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <netdb.h>
  21 #include <pthread.h>
  22 #include <stdlib.h>
  23 #include <gai_misc.h>
  24
  25
  26 struct notify_func
  27   {
  28     void (*func) (sigval_t);
  29     sigval_t value;
  30   };
  31
  32 static void *
  33 notify_func_wrapper (void *arg)
  34 {
  35   gai_start_notify_thread ();
  36   struct notify_func *const n = arg;
  37   void (*func) (sigval_t) = n->func;
  38   sigval_t value = n->value;
  39   free (n);
  40   (*func) (value);
  41   return NULL;
  42 }
  43
  44
  45 int
  46 internal_function
  47 __gai_notify_only (struct sigevent *sigev, pid_t caller_pid)
  48 {
  49   int result = 0;
  50
  51   /* Send the signal to notify about finished processing of the request.  */
  52   if (sigev->sigev_notify == SIGEV_THREAD)
  53     {
  54       /* We have to start a thread.  */
  55       pthread_t tid;
  56       pthread_attr_t attr, *pattr;
  57
  58       pattr = (pthread_attr_t *) sigev->sigev_notify_attributes;
  59       if (pattr == NULL)
  60         {
  61           pthread_attr_init (&attr);
  62           pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
  63           pattr = &attr;
  64         }
  65
  66       /* SIGEV may be freed as soon as we return, so we cannot let the
  67          notification thread use that pointer.  Even though a sigval_t is
  68          only one word and the same size as a void *, we cannot just pass
  69          the value through pthread_create as the argument and have the new
  70          thread run the user's function directly, because on some machines
  71          the calling convention for a union like sigval_t is different from
  72          that for a pointer type like void *.  */
  73       struct notify_func *nf = malloc (sizeof *nf);
  74       if (nf == NULL)
  75         result = -1;
  76       else
  77         {
  78           nf->func = sigev->sigev_notify_function;
  79           nf->value = sigev->sigev_value;
  80           if (pthread_create (&tid, pattr, notify_func_wrapper, nf) < 0)
  81             {
  82               free (nf);
  83               result = -1;
  84             }
  85         }
  86     }
  87   else if (sigev->sigev_notify == SIGEV_SIGNAL)
  88     /* We have to send a signal.  */
  89     if (__gai_sigqueue (sigev->sigev_signo, sigev->sigev_value, caller_pid)
  90         < 0)
  91       result = -1;
  92
  93   return result;
  94 }
  95
  96
  97 void
  98 internal_function
  99 __gai_notify (struct requestlist *req)
 100 {
 101   struct waitlist *waitlist;
 102
 103   /* Now also notify possibly waiting threads.  */
 104   waitlist = req->waiting;
 105   while (waitlist != NULL)
 106     {
 107       struct waitlist *next = waitlist->next;
 108
 109       if (waitlist->sigevp == NULL)
 110         {
 111 #ifdef DONT_NEED_GAI_MISC_COND
 112           GAI_MISC_NOTIFY (waitlist);
 113 #else
 114           /* Decrement the counter.  */
 115           --*waitlist->counterp;
 116
 117           pthread_cond_signal (waitlist->cond);
 118 #endif
 119         }
 120       else
 121         /* This is part of a asynchronous `getaddrinfo_a' operation.  If
 122            this request is the last one, send the signal.  */
 123         if (--*waitlist->counterp == 0)
 124           {
 125             __gai_notify_only (waitlist->sigevp, waitlist->caller_pid);
 126             /* This is tricky.  See getaddrinfo_a.c for the reason why
 127                this works.  */
 128             free ((void *) waitlist->counterp);
 129           }
 130
 131       waitlist = next;
 132     }
 133 }