lib/libc/resolv/mtctxres.c

   1 /*      $NetBSD: mtctxres.c,v 1.4 2007/03/30 20:40:52 ghen Exp $        */
   2
   3 #include <port_before.h>
   4 #ifdef DO_PTHREADS
   5 #include <pthread.h>
   6 #endif
   7 #include <errno.h>
   8 #include <netdb.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <resolv_mt.h>
  12 #include <port_after.h>
  13
  14 #ifdef DO_PTHREADS
  15 static pthread_key_t    key;
  16 static int              mt_key_initialized = 0;
  17
  18 static int              __res_init_ctx(void);
  19 static void             __res_destroy_ctx(void *);
  20
  21 #if defined(sun) && !defined(__GNUC__)
  22 #pragma init    (_mtctxres_init)
  23 #endif
  24 #endif
  25
  26 static mtctxres_t       sharedctx;
  27
  28 #ifdef DO_PTHREADS
  29 /*
  30  * Initialize the TSD key. By doing this at library load time, we're
  31  * implicitly running without interference from other threads, so there's
  32  * no need for locking.
  33  */
  34 static void
  35 _mtctxres_init(void) {
  36         int pthread_keycreate_ret;
  37
  38         pthread_keycreate_ret = pthread_key_create(&key, __res_destroy_ctx);
  39         if (pthread_keycreate_ret == 0)
  40                 mt_key_initialized = 1;
  41 }
  42 #endif
  43
  44 /*
  45  * To support binaries that used the private MT-safe interface in
  46  * Solaris 8, we still need to provide the __res_enable_mt()
  47  * and __res_disable_mt() entry points. They're do-nothing routines.
  48  */
  49 int
  50 __res_enable_mt(void) {
  51         return (-1);
  52 }
  53
  54 int
  55 __res_disable_mt(void) {
  56         return (0);
  57 }
  58
  59 #ifdef DO_PTHREADS
  60 static int
  61 __res_init_ctx(void) {
  62
  63         mtctxres_t      *mt;
  64         int             ret;
  65
  66
  67         if (pthread_getspecific(key) != 0) {
  68                 /* Already exists */
  69                 return (0);
  70         }
  71
  72         if ((mt = malloc(sizeof (mtctxres_t))) == 0) {
  73                 errno = ENOMEM;
  74                 return (-1);
  75         }
  76
  77         memset(mt, 0, sizeof (mtctxres_t));
  78
  79         if ((ret = pthread_setspecific(key, mt)) != 0) {
  80                 free(mt);
  81                 errno = ret;
  82                 return (-1);
  83         }
  84
  85         return (0);
  86 }
  87
  88 static void
  89 __res_destroy_ctx(void *value) {
  90
  91         mtctxres_t      *mt = (mtctxres_t *)value;
  92
  93         if (mt != 0)
  94                 free(mt);
  95 }
  96 #endif
  97
  98 mtctxres_t *
  99 ___mtctxres(void) {
 100 #ifdef DO_PTHREADS
 101         mtctxres_t      *mt;
 102
 103         /*
 104          * This if clause should only be executed if we are linking
 105          * statically.  When linked dynamically _mtctxres_init() should
 106          * be called at binding time due the #pragma above.
 107          */
 108         if (!mt_key_initialized) {
 109                 static pthread_mutex_t keylock = PTHREAD_MUTEX_INITIALIZER;
 110                 if (pthread_mutex_lock(&keylock) == 0) {
 111                         _mtctxres_init();
 112                         (void) pthread_mutex_unlock(&keylock);
 113                 }
 114         }
 115
 116         /*
 117          * If we have already been called in this thread return the existing
 118          * context.  Otherwise recreat a new context and return it.  If
 119          * that fails return a global context.
 120          */
 121         if (mt_key_initialized) {
 122                 if (((mt = pthread_getspecific(key)) != 0) ||
 123                     (__res_init_ctx() == 0 &&
 124                      (mt = pthread_getspecific(key)) != 0)) {
 125                         return (mt);
 126                 }
 127         }
 128 #endif
 129         return (&sharedctx);
 130 }