usr/src/lib/libresolv2/common/resolv/mtctxres.c

   1 /*
   2  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
   3  * Use is subject to license terms.
   4  */
   5
   6
   7 #include <port_before.h>
   8 #ifdef DO_PTHREADS
   9 #include <pthread.h>
  10 #endif
  11 #include <errno.h>
  12 #include <netdb.h>
  13 #include <stdlib.h>
  14 #include <string.h>
  15 #include <resolv_mt.h>
  16 #include <irs.h>
  17 #include <port_after.h>
  18
  19 #ifdef DO_PTHREADS
  20 static pthread_key_t    key;
  21 static int              mt_key_initialized = 0;
  22
  23 static int              __res_init_ctx(void);
  24 static void             __res_destroy_ctx(void *);
  25
  26 #if defined(sun) && !defined(__GNUC__)
  27 #pragma init    (_mtctxres_init)
  28 #endif
  29 #endif
  30
  31 static mtctxres_t       sharedctx;
  32
  33 #ifdef DO_PTHREADS
  34 /*
  35  * Initialize the TSD key. By doing this at library load time, we're
  36  * implicitly running without interference from other threads, so there's
  37  * no need for locking.
  38  */
  39 static void
  40 _mtctxres_init(void) {
  41         int pthread_keycreate_ret;
  42
  43         pthread_keycreate_ret = pthread_key_create(&key, __res_destroy_ctx);
  44         if (pthread_keycreate_ret == 0)
  45                 mt_key_initialized = 1;
  46 }
  47 #endif
  48
  49 /*
  50  * To support binaries that used the private MT-safe interface in
  51  * Solaris 8, we still need to provide the __res_enable_mt()
  52  * and __res_disable_mt() entry points. They're do-nothing routines.
  53  */
  54 int
  55 __res_enable_mt(void) {
  56         return (-1);
  57 }
  58
  59 int
  60 __res_disable_mt(void) {
  61         return (0);
  62 }
  63
  64 #ifdef DO_PTHREADS
  65 static int
  66 __res_init_ctx(void) {
  67
  68         mtctxres_t      *mt;
  69         int             ret;
  70
  71
  72         if (pthread_getspecific(key) != 0) {
  73                 /* Already exists */
  74                 return (0);
  75         }
  76
  77         if ((mt = malloc(sizeof (mtctxres_t))) == 0) {
  78                 errno = ENOMEM;
  79                 return (-1);
  80         }
  81
  82         memset(mt, 0, sizeof (mtctxres_t));
  83
  84         if ((ret = pthread_setspecific(key, mt)) != 0) {
  85                 free(mt);
  86                 errno = ret;
  87                 return (-1);
  88         }
  89
  90         return (0);
  91 }
  92
  93 static void
  94 __res_destroy_ctx(void *value) {
  95
  96         mtctxres_t      *mt = (mtctxres_t *)value;
  97
  98         if (mt != 0)
  99                 free(mt);
 100 }
 101 #endif
 102
 103 mtctxres_t *
 104 ___mtctxres(void) {
 105 #ifdef DO_PTHREADS
 106         mtctxres_t      *mt;
 107
 108         /*
 109          * This if clause should only be executed if we are linking
 110          * statically.  When linked dynamically _mtctxres_init() should
 111          * be called at binding time due the #pragma above.
 112          */
 113         if (!mt_key_initialized) {
 114                 static pthread_mutex_t keylock = PTHREAD_MUTEX_INITIALIZER;
 115                 if (pthread_mutex_lock(&keylock) == 0) {
 116                         _mtctxres_init();
 117                         (void) pthread_mutex_unlock(&keylock);
 118                 }
 119         }
 120
 121         /*
 122          * If we have already been called in this thread return the existing
 123          * context.  Otherwise recreat a new context and return it.  If
 124          * that fails return a global context.
 125          */
 126         if (mt_key_initialized) {
 127                 if (((mt = pthread_getspecific(key)) != 0) ||
 128                     (__res_init_ctx() == 0 &&
 129                      (mt = pthread_getspecific(key)) != 0)) {
 130                         return (mt);
 131                 }
 132         }
 133 #endif
 134         return (&sharedctx);
 135 }