Home | History | Annotate | Line # | Download | only in resolv
mtctxres.c revision 1.1.1.2 
      1 /*	$NetBSD: mtctxres.c,v 1.1.1.2 2007/01/28 02:13:29 christos 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 <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 }
    132