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      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 }
    131