lib/libc/resolv/mtctxres.c

   1 #include <port_before.h>
   2 #ifdef DO_PTHREADS
   3 #include <pthread.h>
   4 #ifdef _LIBC
   5 #include <pthread_np.h>
   6 #endif
   7 #endif
   8 #include <errno.h>
   9 #include <netdb.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include "resolv_mt.h"
  13 #ifndef _LIBC
  14 #include <irs.h>
  15 #endif
  16 #include <port_after.h>
  17
  18 #ifdef DO_PTHREADS
  19 static pthread_key_t    key;
  20 static int              mt_key_initialized = 0;
  21
  22 static int              __res_init_ctx(void);
  23 static void             __res_destroy_ctx(void *);
  24
  25 #if defined(sun) && !defined(__GNUC__)
  26 #pragma init    (_mtctxres_init)
  27 #endif
  28 #endif
  29
  30 static mtctxres_t       sharedctx;
  31
  32 #ifdef DO_PTHREADS
  33 /*
  34  * Initialize the TSD key. By doing this at library load time, we're
  35  * implicitly running without interference from other threads, so there's
  36  * no need for locking.
  37  */
  38 static void
  39 _mtctxres_init(void) {
  40         int pthread_keycreate_ret;
  41
  42         pthread_keycreate_ret = pthread_key_create(&key, __res_destroy_ctx);
  43         if (pthread_keycreate_ret == 0)
  44                 mt_key_initialized = 1;
  45 }
  46 #endif
  47
  48 #ifndef _LIBC
  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 #endif
  59
  60 int
  61 __res_disable_mt(void) {
  62         return (0);
  63 }
  64
  65 #ifdef DO_PTHREADS
  66 static int
  67 __res_init_ctx(void) {
  68
  69         mtctxres_t      *mt;
  70         int             ret;
  71
  72
  73         if (pthread_getspecific(key) != 0) {
  74                 /* Already exists */
  75                 return (0);
  76         }
  77
  78         if ((mt = malloc(sizeof (mtctxres_t))) == NULL) {
  79                 errno = ENOMEM;
  80                 return (-1);
  81         }
  82
  83         memset(mt, 0, sizeof (mtctxres_t));
  84
  85         if ((ret = pthread_setspecific(key, mt)) != 0) {
  86                 free(mt);
  87                 errno = ret;
  88                 return (-1);
  89         }
  90
  91         return (0);
  92 }
  93
  94 static void
  95 __res_destroy_ctx(void *value) {
  96
  97         mtctxres_t      *mt = (mtctxres_t *)value;
  98
  99         if (mt != NULL)
 100                 free(mt);
 101 }
 102 #endif
 103
 104 mtctxres_t *
 105 ___mtctxres(void) {
 106 #ifdef DO_PTHREADS
 107         mtctxres_t      *mt;
 108
 109 #ifdef _LIBC
 110         if (pthread_main_np() != 0)
 111                 return (&sharedctx);
 112 #endif
 113
 114
 115         /*
 116          * This if clause should only be executed if we are linking
 117          * statically.  When linked dynamically _mtctxres_init() should
 118          * be called at binding time due the #pragma above.
 119          */
 120         if (!mt_key_initialized) {
 121                 static pthread_mutex_t keylock = PTHREAD_MUTEX_INITIALIZER;
 122                 if (pthread_mutex_lock(&keylock) == 0) {
 123                         _mtctxres_init();
 124                         (void) pthread_mutex_unlock(&keylock);
 125                 }
 126         }
 127
 128         /*
 129          * If we have already been called in this thread return the existing
 130          * context.  Otherwise recreat a new context and return it.  If
 131          * that fails return a global context.
 132          */
 133         if (mt_key_initialized) {
 134                 if (((mt = pthread_getspecific(key)) != NULL) ||
 135                     (__res_init_ctx() == 0 &&
 136                      (mt = pthread_getspecific(key)) != NULL)) {
 137                         return (mt);
 138                 }
 139         }
 140 #endif
 141         return (&sharedctx);
 142 }