contrib/bind-9.5.2/lib/bind/resolv/mtctxres.c

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