external/bsd/libbind/dist/resolv/mtctxres.c

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