lib/libpthread/res_state.c

   1 /*      $NetBSD: res_state.c,v 1.5 2007/11/13 15:57:14 ad Exp $ */
   2
   3 /*-
   4  * Copyright (c) 2004 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Christos Zoulas.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  29  * POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <sys/cdefs.h>
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 __RCSID("$NetBSD: res_state.c,v 1.5 2007/11/13 15:57:14 ad Exp $");
  35 #endif
  36
  37 #include <sys/types.h>
  38 #include <sys/queue.h>
  39 #include <arpa/inet.h>
  40 #include <arpa/nameser.h>
  41 #include <stdlib.h>
  42 #include <unistd.h>
  43 #include <resolv.h>
  44 #include <netdb.h>
  45
  46 #include "pthread.h"
  47 #include "pthread_int.h"
  48
  49 static SLIST_HEAD(, _res_st) res_list = LIST_HEAD_INITIALIZER(&res_list);
  50
  51 struct _res_st {
  52         /* __res_put_state() assumes st_res is the first member. */
  53         struct __res_state      st_res;
  54
  55         SLIST_ENTRY(_res_st)    st_list;
  56 };
  57
  58 static pthread_mutex_t res_mtx = PTHREAD_MUTEX_INITIALIZER;
  59
  60 res_state __res_state(void);
  61 res_state __res_get_state(void);
  62 void __res_put_state(res_state);
  63
  64 #ifdef RES_STATE_DEBUG
  65 static void
  66 res_state_debug(const char *msg, void *p)
  67 {
  68         char buf[512];
  69         pthread_t self = pthread__self();
  70         int len = snprintf(buf, sizeof(buf), "%p: %s %p\n", self, msg, p);
  71
  72         (void)write(STDOUT_FILENO, buf, (size_t)len);
  73 }
  74 #else
  75 #define res_state_debug(a, b)
  76 #endif
  77
  78
  79 res_state
  80 __res_get_state(void)
  81 {
  82         res_state res;
  83         struct _res_st *st;
  84         pthread_mutex_lock(&res_mtx);
  85         st = SLIST_FIRST(&res_list);
  86         if (st != NULL) {
  87                 SLIST_REMOVE_HEAD(&res_list, st_list);
  88                 pthread_mutex_unlock(&res_mtx);
  89                 res = &st->st_res;
  90                 res_state_debug("checkout from list", st);
  91         } else {
  92                 pthread_mutex_unlock(&res_mtx);
  93                 st = malloc(sizeof(*st));
  94                 if (st == NULL) {
  95                         h_errno = NETDB_INTERNAL;
  96                         return NULL;
  97                 }
  98                 res = &st->st_res;
  99                 res->options = 0;
 100                 res_state_debug("alloc new", res);
 101         }
 102         if ((res->options & RES_INIT) == 0) {
 103                 if (res_ninit(res) == -1) {
 104                         h_errno = NETDB_INTERNAL;
 105                         free(st);
 106                         return NULL;
 107                 }
 108         }
 109         return res;
 110 }
 111
 112 void
 113 /*ARGSUSED*/
 114 __res_put_state(res_state res)
 115 {
 116         struct _res_st *st = (struct _res_st *)(void *)res;
 117
 118         res_state_debug("free", res);
 119         pthread_mutex_lock(&res_mtx);
 120         SLIST_INSERT_HEAD(&res_list, st, st_list);
 121         pthread_mutex_unlock(&res_mtx);
 122 }
 123
 124 /*
 125  * This is aliased via a macro to _res; don't allow multi-threaded programs
 126  * to use it.
 127  */
 128 res_state
 129 __res_state(void)
 130 {
 131         static const char res[] = "_res is not supported for multi-threaded"
 132             " programs.\n";
 133         (void)write(STDERR_FILENO, res, sizeof(res) - 1);
 134         abort();
 135         return NULL;
 136 }